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1 <html>
2 <head>
3 <meta name="author" content="Christian Schoenebeck">
4 <title>NKSP Language</title>
5 <meta name="description" content="Introduction to the NKSP real-time instrument script language.">
6 </head>
7 <body>
8 <p>
9 This document intends to give you a compact introduction and overview to
10 the NKSP real-time instrument script language, so you can start writing
11 your own instrument scripts in short time. It concentrates on describing
12 the script language. If you rather want to learn how to modify and
13 attach scripts to your sounds, then please refer to the gigedit manual for
14 <a href="gigedit_scripts.html">how to manage instrument scripts with gigedit</a>.
15 </p>
16
17 <h3>At a Glance</h3>
18 <p>
19 <img src="nksp_file.png" style="height:111px; margin-right:12px;">
20 NKSP stands for "is <b>N</b>ot <b>KSP</b>", which denotes its distinction
21 to an existing proprieatary language called <i>KSP</i>.
22 NSKP is a script language specifically designed to write real-time capable
23 software extensions to LinuxSampler's sampler engines that can be bundled
24 individually with sounds by sound designers themselves.
25
26 Instead of defining a completely new script language, NKSP is leaned on
27 that mentioned properiatary script language. The biggest advantage is that
28 sound designers and musicians can leverage the huge amount of existing KSP
29 scripts which are already available for various purposes on the Internet,
30 instead of being forced to write all scripts from scratch in a completely
31 different language.
32 </p>
33 <p>
34 That also means however that there are some differences between those two
35 languages. Some extensions have been added to the NKSP core language to
36 make it a bit more convenient and less error prone to write scripts, and
37 various new functions had to be added due to the large difference of the
38 sampler engines and their underlying sampler format. Efforts have been
39 made though to make NKSP as much compatible to KSP as possible.
40 The NKSP documentation will emphasize individual differences in
41 the two languages and function implementations wherever they may occur, to
42 give you immediate hints where you need to take care of regarding
43 compatibility issues when writing scripts that should be spawned on both
44 platforms.
45 </p>
46 <p>
47 Please note that the current focus of NKSP is the sound controlling aspect
48 of sounds. At this point there is no support for the graphical user
49 interface function set of KSP in NKSP.
50 </p>
51
52 <h2>Event Handlers</h2>
53 <p>
54 NKSP is an event-driven language. That means you are writing so called
55 <i>event handlers</i> which define what the sampler shall do on individual
56 events that occur, while using the sound the script was bundled with.
57 An event handler in general looks like this:
58 </p>
59 <code lang="nksp">
60 on ??event-name??
61
62 ??statements??
63
64 end on
65 </code>
66 <p>
67 There are currently four events available:
68 </p>
69 <table>
70 <tr>
71 <th>Event Type</th> <th>Description</th>
72 </tr>
73 <tr>
74 <td><code>on note</code></td> <td>This event handler is executed when a new note was triggered, i.e. when hitting a key on a MIDI keyboard.</td>
75 </tr>
76 <tr>
77 <td><code>on release</code></td> <td>This event handler is executed when a new note was released, i.e. when releasing a key on a MIDI keyboard.</td>
78 </tr>
79 <tr>
80 <td><code>on controller</code></td> <td>This event handler is executed when a MIDI control change event occurred. For instance when turning the modulation wheel at a MIDI keyboard.</td>
81 </tr>
82 <tr>
83 <td><code>on init</code></td> <td>Executed only once, as very first event handler, right after the script had been loaded. This code block is usually used to initialize variables in your script with some initial, useful data.</td>
84 </tr>
85 </table>
86 <p>
87 You are free to decide for which ones of those event types you are going to
88 write an event handler for. You can write an event handler for only one
89 event type or write event handlers for all of those event types. Also
90 dependent on the respective event type, there are certain things you can
91 do and things which you can't do. But more on that later.
92 </p>
93
94 <h3>Note Events</h3>
95 <p>
96 As a first example, the following tiny script will print a message to your
97 terminal whenever you trigger a new note with your MIDI keyboard.
98 </p>
99 <code>
100 on note
101 message("A new note was triggered!")
102 end on
103 </code>
104 <p>
105 Probably you are also interested to see which note you triggered exactly.
106 The sampler provides you a so called
107 <i title="A script variable which is provided by the sampler and which has a very specific purpose which you cannot override for other purposes.">
108 built-in variable
109 </i>
110 called <code>$EVENT_NOTE</code> which reflects the note number
111 (as value between 0 and 127) of the note that has just been triggered. Additionally
112 the built-in variable <code>$EVENT_VELOCITY</code> provides you the
113 velocity value (also between 0 and 127) of the note event.
114 </p>
115 <code>
116 on note
117 message("Note " & $EVENT_NOTE & " was triggered with velocity " & $EVENT_VELOCITY)
118 end on
119 </code>
120 <p>
121 The <code>&</code> character concatenates text strings with each other.
122 In this case it is also automatically converting the note number into a
123 text string.
124 </p>
125 <note class="important">
126 The message() function is not appropriate for being used with your final
127 production sounds, since it can lead to audio dropouts.
128 You should only use the message() function to try out things, and to spot
129 and debug problems with your scripts.
130 </note>
131
132 <h3>Release Events</h3>
133 <p>
134 As counter part to the <code>note</code> event handler, there is also the
135 <code>release</code> event handler, which is executed when a note was
136 released. This event handler can be used similarly:
137 </p>
138 <code>
139 on release
140 message("Note " & $EVENT_NOTE & " was released with release velocity " & $EVENT_VELOCITY)
141 end on
142 </code>
143 <p>
144 Please note that you can hardly find MIDI keyboards which support release
145 velocity. So with most keyboards this value will be 127.
146 </p>
147
148 <h3>Controller Events</h3>
149 <p>
150 Now let's extend the first script to not only show note-on and note-off
151 events, but also to show a message whenever
152 you use a MIDI controller (i.e. modulation wheel, sustain pedal, etc.).
153 </p>
154 <code>
155 on note
156 message("Note " & $EVENT_NOTE & " was triggered with velocity " & $EVENT_VELOCITY)
157 end on
158
159 on release
160 message("Note " & $EVENT_NOTE & " was released with release velocity " & $EVENT_VELOCITY)
161 end on
162
163 on controller
164 message("MIDI Controller " & $CC_NUM " changed its value to " & %CC[$CC_NUM])
165 end on
166 </code>
167 <p>
168 It looks very similar to the note event handlers. <code>$CC_NUM</code>
169 reflects the MIDI controller number of the MIDI controller that had been
170 changed and <code>%CC</code> is a so called <i>array variable</i>, which not only
171 contains a single number value, but instead it contains several values at
172 the same time. The built-in <code>%CC</code> array variable contains the current
173 controller values of all 127 MIDI controllers. So <code>%CC[1]</code> for
174 example would give you the current controller value of the modulation
175 wheel, and therefore <code>%CC[$CC_NUM]</code> reflects the new controller
176 value of the controller that just had been changed.
177 </p>
178 <p>
179 There is some special aspect you need to be aware about: in contrast to the MIDI standard,
180 monophonic aftertouch (a.k.a. channel pressure) and pitch beend wheel are
181 handled by NKSP as if they were regular MIDI controllers. So a value change
182 of one of those two triggers a regular <code>controller</code> event handler
183 to be executed. To obtain the current aftertouch value you can use
184 <code>%CC[$VCC_MONO_AT]</code>, and to get the current pitch bend wheel
185 value use <code>%CC[$VCC_PITCH_BEND]</code>.
186 </p>
187
188 <h3>Script Load Event</h3>
189 <p>
190 As the last one of the four event types available with NKSP, the following
191 is an example of an <code>init</code> event handler.
192 </p>
193 <code>
194 on init
195 message("This script has been loaded and is ready now!")
196 end on
197 </code>
198 <p>
199 You might think, that this is probably a very exotic event. Because in
200 fact, this "event" is only executed once for your script: exactly when
201 the script was loaded by the sampler. This is not an unimportant event
202 handler though. Because it is used to prepare your script for various
203 purposes. We will get more about that later.
204 </p>
205
206 <h2>Comments</h2>
207 <p>
208 Let's face it: software code is sometimes hard to read, especially when you
209 are not a professional software developer who deals with such kinds of
210 things every day. To make it more easy for you to understand, what you
211 had in mind when you wrote a certain script three years ago, and also if
212 some other developer might need to continue working on your scripts one
213 day, you should place as many comments into your scripts as possible. A
214 comment in NKSP is everything that is nested into a an opening and closing
215 pair of curly braces.
216 </p>
217 <code>{ This is a comment. }</code>
218 <p>
219 You cannot only use this to leave some human readable explanations here
220 and there, you might also use such curly braces to quickly disable parts
221 of your scripts for a moment, i.e. when debugging certain things.
222 </p>
223 <code>
224 on init
225 { The following will be prompted to the terminal when the sampler loaded this script. }
226 message("My script loaded.")
227
228 { This code block is commented out, so these two messages will not be displayed }
229 {
230 message("Another text")
231 message("And another one")
232 }
233 end on
234 </code>
235
236 <h2>Variables</h2>
237 <p>
238 In order to be able to write more complex and more useful scripts, you
239 also need to remember some data somewhere for being able to use that
240 data at a later point. This can be done by using
241 <i title="A variable is a storage location paired with an associated symbolic name.">
242 variables
243 </i>.
244 We already came across some <i>built-in variables</i>, which are already
245 defined by the sampler for you. To store your own data you need to declare
246 your own <i>user variables</i>, which has the following form:
247 </p>
248 <p>
249 <code>declare $??variable-name?? := ??initial-value??
250 </p>
251 <p>
252 The left hand side's <code>??variable-name??</code> is an arbitrary name
253 you can chose for your variable. That name might consist of English
254 letters A to Z (lower and upper case) and the underscore character "<code>_</code>".
255 Variable names must be unique. So you can neither declare several variables
256 with the same name, nor can you use a name for your variable that is
257 already been reserved by <i>built-in variables</i>.
258 The right hand side's <code>??initial-value??</code> is simply the first
259 value the variable should store right after it was created. You can also
260 omit that.
261 </p>
262 <p>
263 <code>declare $??variable-name??
264 </p>
265 <p>
266 In that case the sampler will automatically assign <code>0</code> for you
267 as the variable's initial value. This way we could for example count the
268 total amount of notes triggered.
269 </p>
270 <code>
271 on init
272 declare $numberOfNotes := 0
273 end on
274
275 on note
276 $numberOfNotes := $numberOfNotes + 1
277
278 message("This is the " & $numberOfNotes & "th note triggered so far.")
279 end on
280 </code>
281 <p>
282 In the <code>init</code> event handler we create our own variable
283 <code>$numberOfNotes</code> and assign <code>0</code> to it as its
284 initial value. Like mentioned before, that initial assignment is optional.
285 In the <code>note</code> event handler we then increase the
286 <code>$numberOfNotes</code> variable by one, each time a new note was
287 triggered and then print a message to the terminal with the current total
288 amount of notes that have been triggered so far.
289 </p>
290 <note>
291 NKSP allows you to declare variables in all event handlers, however if
292 you want to keep compatibility with KSP, then you should only
293 declare variables in <code>init</code> event handlers.
294 </note>
295
296 <h3>Variable Types</h3>
297 <p>
298 There are currently three different variable types, which you can easily
299 recognize upon their first character.
300 </p>
301 <table>
302 <tr>
303 <th>Variable Form</th> <th>Data Type</th> <th>Description</th>
304 </tr>
305 <tr>
306 <td><code>$??variable-name??</code></td> <td>Integer Scalar</td> <td>Stores one single integer number value.</td>
307 </tr>
308 <tr>
309 <td><code>%??variable-name??</code></td> <td>Integer Array</td> <td>Stores a certain amount of integer number values.</td>
310 </tr>
311 <tr>
312 <td><code>@??variable-name??</code></td> <td>String</td> <td>Stores one text string.</td>
313 </tr>
314 </table>
315 <p>
316 So the first character just before the actual variable name, always
317 denotes the data type of the variable. Also note that all variable types
318 share the same variable name space. That means you cannot declare a
319 variable with a name that has already been used to declare a variable of
320 another variable type.
321 </p>
322
323 <h3>Array Variables</h3>
324 <p>
325 We already used the first two variable types. However we have not seen yet
326 how to declare such array variables. This is the common declaration form
327 for creating your own array variables.
328 </p>
329 <code>
330 on init
331 declare %??variable-name??[??array-size??] := ( ??list-of-values?? )
332 end on
333 </code>
334 <p>
335 So let's say you wanted to create an array variable with the first 12
336 prime numbers, then it might look like this.
337 </p>
338 <code>
339 on init
340 declare %primes[12] := ( 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37 )
341 end on
342 </code>
343 <p>
344 Like with integer variables, assigning some initial values with
345 <code>??list-of-values??</code> is optional. The array
346 declaration form without initial value assignment looks like this.
347 </p>
348 <code>
349 on init
350 declare %??variable-name??[??array-size??]
351 end on
352 </code>
353 <p>
354 When you omit that initial assignment, then all numbers of that array will
355 automatically be initialized with <code>0</code> each. With array
356 variables however, it is always mandatory to provide
357 <code>??array-size??</code> with an array
358 variable declaration, so the sampler can create that array with the
359 requested amount of values when the script is loaded. In contrast to many
360 other programming languages, changing that amount of values of an array
361 variable is not possible after the variable had been declared. That's due
362 to the fact that this language is dedicated to real-time applications, and
363 changing the size of an array variable at runtime would harm real-time
364 stability of the sampler and thus could lead to audio dropouts. So NKSP
365 does not allow you to do that.
366 </p>
367
368
369 <h3>String Variables</h3>
370 <p>
371 You might also store text with variables. These are called <i>text string
372 variables</i>, or short: <i>string variables</i>. Let's skip the common declaration
373 form of string variables and let us modify a prior example to just use
374 such kind of variable.
375 </p>
376 <code>
377 on init
378 declare $numberOfNotes
379 declare @firstText := "This is the "
380 declare @secondText
381 end on
382
383 on note
384 $numberOfNotes := $numberOfNotes + 1
385 @secondText := "th note triggered so far."
386 message(@firstText & $numberOfNotes & @secondText)
387 end on
388 </code>
389 <p>
390 It behaves exactly like the prior example and shall just give you a
391 first idea how to declare and use string variables.
392 </p>
393 <note class="important">
394 Like with the message() function, you should not use string variables
395 with your final production sounds, since it can lead to audio dropouts.
396 You should only use string variables to try out things, and to spot
397 and debug problems with your scripts.
398 </note>
399
400 <h3>Variable Scope</h3>
401 <p>
402 By default, all variables you declare with NKSP are
403 <i title="A variable that is accessible throughout an entire script.">
404 global variables
405 </i>. That means every event handler can access the data of such a global
406 variable. Furthermore, each instance of an event handler accesses the same
407 data when it is referencing that variable. And the latter fact can be a
408 problem sometimes, which we will outline next.
409 </p>
410 <p>
411 Let's assume you wanted to write an instrument script that shall resemble
412 a simple delay effect. You could do that by writing an note event handler
413 that automatically triggers several new notes for each note being
414 triggered on a MIDI keyboard. The following example demonstrates how that
415 could be achieved.
416 </p>
417 <note class="important">
418 The following example does not fully work with LinuxSampler yet. That's
419 because the used <code>wait()</code> function is not fully implemented
420 yet. Currently a <code>wait()</code> function call suspends execution,
421 but since the respective scheduler code is yet missing, the script
422 will automatically be resumed with the next audio fragment cycle. So
423 effectively a <code>wait()</code> call will pause your script for a few
424 miliseconds with LinuxSampler right now, no matter which function argument
425 you provided. Hopefully this will be implemented soon though.
426 </note>
427 <code>
428 on init
429 { The amount of notes to play }
430 declare const $delayNotes := 4
431 { Tempo with which the new notes will follow the orignal note }
432 declare const $bpm := 90
433 { Convert BPM to microseconds (duration between the notes) }
434 declare const $delayMicroSeconds := 60 * 1000000 / $bpm
435 { Just a working variable for being used with the while loop below }
436 declare $i
437 { For each successive note we trigger, we will reduce the velocity a bit}
438 declare $velocity
439 end on
440
441 on note
442 { First initialize the variable $i with 4 each time we enter this event
443 handler, because each time we executed this handler, the variable will be 0 }
444 $i := $delayNotes
445
446 { Loop which will be executed 4 times in a row }
447 while ($i)
448 { Calculate the velocity for the next note being triggered }
449 $velocity := 127 * $i / ($delayNotes + 1)
450 { Suspend this script for a short moment ... }
451 wait($delayMicroSeconds)
452 { ... and after that short break, trigger a new note. }
453 play_note($EVENT_NOTE, $velocity)
454 { Decrement loop counter $i by one }
455 $i := $i - 1
456 end while
457 end on
458 </code>
459 <p>
460 In this example we used a new keyword <code>const</code>. This additional
461 variable qualifier defines that we don't intend to change this variable
462 after declaration. So if you know beforehand, that a certain variable should
463 remain with a certain value, then you might use the <code>const</code>
464 qualifier to avoid that you i.e. change the value accidently when you
465 modify the script somewhere in future.
466 </p>
467 <p>
468 Now when you trigger one single note on your keyboard with that script,
469 you will hear the additional notes being triggered. And also when you
470 hit another note after a while, everything seems to be fine. However if
471 you start playing quick successive notes, you will notice something goes
472 wrong. The amount of notes being triggered by the script is now incorrect
473 and also the volume of the individual notes triggered by the script is wrong.
474 What's going on?
475 </p>
476 <p>
477 To understand the problem in the last example, let's consider what is
478 happening when executing that script exactly: Each time you play a note
479 on your keyboard, a new instance of the <code>note</code> event handler
480 will be spawned and executed by the sampler. In all our examples so far
481 our scripts were so simple, that in practice only one handler instance
482 was executed at a time. This is different in this case though. Because
483 by calling the <code>wait()</code> function, the respective handler
484 execution instance is paused for a while and in total each handler
485 instance will be executed for more than 2 seconds in this particular
486 example. As a consequence, when
487 you play multiple, successive notes on your keyboard in short time, you
488 will have several instances of the <code>note</code> event handler running
489 simultaniously. And that's where the problem starts. Because by default,
490 as said, all variables are global variables. So the handler instances
491 which are now running in parallel, are all reading and modifying the same
492 data. Thus the individual handler instances will modify the
493 <code>$i</code> and <code>$velocity</code> variables of each other, causing
494 an undesired misbehavior.
495 </p>
496 <note>
497 NKSP's built-in function <code>play_note()</code> allows you to pass
498 between one and four function arguments. For the function arguments you
499 don't provide to a <code>play_note()</code> call, NKSP will automatically
500 use default values. If you want your script to be compatible with KSP,
501 then you should always pass four arguments to that function though.
502 </note>
503
504 <h3>Polyphonic Variables</h3>
505 <p>
506 As a logical consequence of the previously described data concurrency
507 problem, it would be desirable to have each event handler instance use
508 its own variable instance, so that the individual handler instances stop
509 interfering with each other. For this purpose the so called
510 <i title="A variable which is effectively a separate variable for each event handler instance.">
511 polyphonic variable
512 </i>
513 qualifier exists with NKSP. Declaring such a variable is identical to
514 declaring a regular variable, just that you add the keyword <code>polyphonic</code>.
515 </p>
516 <code>
517 declare polyphonic $??variable-name??
518 </code>
519 <p>
520 So to fix the bug in our previous example, we simply make the variables
521 <code>$i</code> and <code>$velocity</code> polyphonic variables.
522 </p>
523 <code>
524 on init
525 { The amount of notes to play }
526 declare const $delayNotes := 4
527 { Tempo with which the new notes will follow the orignal note }
528 declare const $bpm := 90
529 { Convert BPM to microseconds (duration between the notes) }
530 declare const $delayMicroSeconds := 60 * 1000000 / $bpm
531 { Just a working variable for being used with the while loop below }
532 declare polyphonic $i { < --- NOW POLYPHONIC !!! }
533 { For each successive note we trigger, we will reduce the velocity a bit}
534 declare polyphonic $velocity { < --- NOW POLYPHONIC !!! }
535 end on
536
537 on note
538 { First initialize the variable $i with 4 each time we enter this event
539 handler, because each time we executed this handler, the variable will be 0 }
540 $i := $delayNotes
541
542 { Loop which will be executed 4 times in a row }
543 while ($i)
544 { Calculate the velocity for the next note being triggered }
545 $velocity := 127 * $i / ($delayNotes + 1)
546 { Suspend this script for a short moment ... }
547 wait($delayMicroSeconds)
548 { ... and after that short break, trigger a new note. }
549 play_note($EVENT_NOTE, $velocity)
550 { Decrement loop counter $i by one }
551 $i := $i - 1
552 end while
553 end on
554 </code>
555 <p>
556 And that's it! The script works now as intended. Now you might wonder, why
557 are variables not <i>polyphonic</i> by default? Isn't that more common and
558 wouldn't that be more safer than using global variables by default? The reason is that
559 a polyphonic variable consumes a lot more memory than a regular (global) variable.
560 That's because for each polyphonic variable, the sampler has to allocate
561 in advance (when the script is loaded) as many instances of that
562 polyphonic variable as there are maximum events
563 allowed with the sampler. So that's a lot! Considering that today's
564 computers have plenty of RAM this might be a theoretical aspect, but in the
565 end: this default scope of variables was already like this with <i>KSP</i>
566 so we are also doing it like this with NKSP for compatibility reasons.
567 </p>
568 <p>
569 Please note that the <i>polyphonic</i> qualifier only exists for integer
570 variables. So you cannot declare polyphonic string variables, nor can you
571 declare polyphonic array variables. Like in the previous explanation,
572 this is due to the fact that it would consume a huge amount of memory
573 for such variables. And with string variables and array variables, the
574 required amount of memory would be much higher than with simple integer
575 variables.
576 </p>
577 <p>
578 As summary, the following are guideline rules describing when you should
579 use the polyphonic qualifier for a certain variable. You should declare
580 a particular variable polyphonic if one (or even both) of the following two
581 conditions apply to that variable.
582 </p>
583 <ol>
584 <li>
585 If you call the <code>wait()</code> function within your event
586 handlers and the respective variable is modified and read before
587 and after at least one of the individual <code>wait()</code> calls.
588 </li>
589 <li>
590 If you have loops that might run for a very long time, while accessing
591 the respective variable in between. That's because if your script is
592 running consecutively for too long, the sampler will automatically suspend your
593 script for a while to avoid your script becoming a real-time stability
594 hazard for the sampler. Your script will then automatically be resumed
595 after a short moment by the sampler, so effectively this is similar to
596 something like an "automated" <code>wait()</code> function call by
597 the sampler.
598 </li>
599 </ol>
600 <p>
601 In all other cases you should rather use regular (global) variables instead.
602 But keep in mind that you might need to re-assign a certain value for
603 some global variables when you enter the respective event handler, just
604 like we did with <code>$i := $delayNotes</code> right from the start
605 during discussion of the previous example script.
606 </p>
607
608 <h2>Control Structures</h2>
609 <p>
610 A computer is more than a calculator that adds numbers and stores them
611 somewhere. One of the biggest strength of a computer, which makes it
612 such powerful, is the ability to do different things depending on various
613 conditions. For example your computer might clean up your hard drive
614 while you are not sitting in front of it, and it might immediately stop
615 doing so when you need all its resources to cut your latest video which
616 you just shot.
617 </p>
618 <p>
619 In order to do that for you, a computer program allows you to define
620 conditions and a list of instructions the computer shall
621 perform for you under those individual conditions. These kinds of
622 software mechanisms are called <i>Control Structures</i>.
623 </p>
624
625 <h3>if Branches</h3>
626 <p>
627 The most fundamental control structure are <i>if branches</i>, which has
628 the following general form.
629 </p>
630 <code>
631 if (??condition??)
632
633 ??statements??
634
635 end if
636 </code>
637 <p>
638 The specified <code>??condition??</code> is evaluated each time script
639 execution reaches this control block. The condition can for example be
640 the value of a variable, some arithmetic expression, a function call or
641 a combination of them. In all cases the sampler expects the
642 <code>??condition??</code> expression to evaluate to some numeric
643 (or boolean) value. If the evaluated number is exactly <code>0</code> then
644 the condition is interpreted to be <i>false</i> and thus the list of
645 <code>??statements??</code> is not executed. If the evaluated value is any
646 other value than <code>0</code> then the condition is interpreted to be
647 <i>true</i> and accordingly the list of <code>??statements??</code> will be
648 executed.
649 </p>
650 <p>
651 Alternatively you might also specify a list of instructions which shall be
652 executed when the condition is <i>false</i>.
653 </p>
654 <code>
655 if (??condition??)
656
657 ??statements-when-true??
658
659 else
660
661 ??statements-when-false??
662
663 end if
664 </code>
665 <p>
666 In this case the first list of statements is executed when the
667 <code>??condition??</code> evaluated to <i>true</i>, otherwise the second
668 list of statements is executed instead.
669 </p>
670 <p>
671 Once again, let's get back to the example of counting triggered notes.
672 You might have noticed that it did not output correct English for the
673 first three notes. Let's correct this now.
674 </p>
675 <code>
676 on init
677 declare $numberOfNotes
678 declare @postfix
679 end on
680
681 on note
682 $numberOfNotes := $numberOfNotes + 1
683
684 if ($numberOfNotes == 1)
685 @postfix := "st"
686 else
687 if ($numberOfNotes == 2)
688 @postfix := "nd"
689 else
690 if ($numberOfNotes == 3)
691 @postfix := "rd"
692 else
693 @postfix := "th"
694 end if
695 end if
696 end if
697
698 message("This is the " & $numberOfNotes & @postfix & " note triggered so far.")
699 end on
700 </code>
701 <p>
702 We are now checking the value of <code>$numberOfNotes</code> before we
703 print out a message. If <code>$numberOfNotes</code> equals one, then we
704 assign the string <code>"st"</code> to the variable <code>@postfix</code>,
705 if <code>$numberOfNotes</code> equals 2 instead we assign the string
706 <code>"nd"</code> instead, if it equals 3 instead we assign
707 <code>"rd"</code>, in all other cases we assign the string
708 <code>"th"</code>. And finally we assemble the text message to be
709 printed out to the terminal on line 23.
710 </p>
711
712 <h3>Select Case Branches</h3>
713 <p>
714 The previous example now outputs the numbers in correct English. But the
715 script code looks a bit bloated, right? That's why there is a short hand
716 form.
717 </p>
718 <code>
719 select ??expression??
720
721 case ??integer-1??
722
723 ??statements-1??
724
725
726 case ??integer-2??
727
728 ??statements-2??
729
730 .
731 .
732 .
733 end select
734 </code>
735 <p>
736 The provided <code>??expression??</code> is first evaluated to an integer
737 value. Then this value is compared to the integer values of the nested
738 <code>case</code> lines. So it first compares the evaluated value of
739 <code>??expression??</code> with <code>??integer-1??</code>, then it
740 compares it with <code>??integer-2??</code>, and so on. The first integer
741 number that matches with the evaluated value of <code>??expression??</code>,
742 will be interpreted as being the current valid condition. So if
743 <code>??expression??</code> equals <code>??integer-1??</code>,
744 then <code>??statements-1??</code> will be executed, otherwise if
745 <code>??expression??</code> equals <code>??integer-2??</code>,
746 then <code>??statements-2??</code> will be executed, and so on.
747 </p>
748 <p>
749 Using a select-case construct, our previous example would look like follows.
750 </p>
751 <code>
752 on init
753 declare $numberOfNotes
754 declare @postfix
755 end on
756
757 on note
758 $numberOfNotes := $numberOfNotes + 1
759 @postfix := "th"
760
761 select $numberOfNotes
762 case 1
763 @postfix := "st"
764 case 2
765 @postfix := "nd"
766 case 3
767 @postfix := "rd"
768 end if
769
770 message("This is the " & $numberOfNotes & @postfix & " note triggered so far.")
771 end on
772 </code>
773 <note>
774 If you like, you can also put parentheses around the select expression,
775 like <code>select (??expression??)</code>. Some developers familiar with
776 other programming languages might prefer this style. However if you want
777 to keep compatibility with KSP, you should not use parentheses for
778 select expressions.
779 </note>
780 <p>
781 The amount
782 of case conditions you add to such select-case blocks is completely up
783 to you. Just remember that the case conditions will be compared one by one,
784 from top to down. The latter can be important when you define a case line
785 that defines a value range. So for instance the following example will
786 not do what was probably intended.
787 </p>
788 <code>
789 on init
790 declare $numberOfNotes
791 end on
792
793 on note
794 $numberOfNotes := $numberOfNotes + 1
795
796 select $numberOfNotes
797 case 1 to 99
798 message("Less than 100 notes triggered so far")
799 exit
800 case 1
801 message("First note was triggered!") { Will never be printed ! }
802 exit
803 case 2
804 message("Second note was triggered!") { Will never be printed ! }
805 exit
806 case 3
807 message("Third note was triggered!") { Will never be printed ! }
808 exit
809 end if
810
811 message("Wow, already the " & $numberOfNotes & "th note triggered.")
812 end on
813 </code>
814 <p>
815 You probably get the idea what this script "should" do. For the 1st note
816 it should print <code>"First note was triggered!"</code>, for the 2nd
817 note it should print <code>"Second note was triggered!"</code>, for the 3rd
818 note it should print <code>"Third note was triggered!"</code>, for the 4th
819 up to 99th note it should print <code>"Less than 100 notes triggered so far"</code>,
820 and starting from the 100th note and all following ones, it should print
821 the precise note number according to line 23. However, it doesn't!
822 </p>
823 <p>
824 To correct this problem, you need to move the first case block to the end,
825 like follows.
826 </p>
827 <code>
828 on init
829 declare $numberOfNotes
830 end on
831
832 on note
833 $numberOfNotes := $numberOfNotes + 1
834
835 select $numberOfNotes
836 case 1
837 message("First note was triggered!")
838 exit
839 case 2
840 message("Second note was triggered!")
841 exit
842 case 3
843 message("Third note was triggered!")
844 exit
845 case 1 to 99
846 message("Less than 100 notes triggered so far")
847 exit
848 end if
849
850 message("Wow, already the " & $numberOfNotes & "th note triggered.")
851 end on
852 </code>
853 <p>
854 Or you could of course fix the questioned case range from <code>case 1 to 99</code>
855 to <code>case 4 to 99</code>. Both solutions will do.
856 </p>
857 <p>
858 We also used the <i>built-in function</i> <code>exit()</code> in the
859 previous example. You can use it to stop execution at that point of your
860 script. In the previous example it prevents multiple messages to be
861 printed to the terminal.
862 </p>
863 <note class="important">
864 The <code>exit()</code> function only stops execution of the <b>current</b>
865 event handler instance! It does <b>not</b> stop execution of other
866 instances of the same event handler, nor does it stop execution of other
867 handlers of other event types, and especially it does <b>not</b> stop or
868 prevent further or future execution of your entire script! In other words,
869 you should rather see this function as a return statement, in case you are
870 familiar with other programming languages already.
871 </note>
872
873 <h3>while Loops</h3>
874 <p>
875 Another fundamental control construct of program flow are loops.
876 You can use so called
877 <i title="Repeats a given list of instructions until the defined condition turns false.">
878 while loops
879 </i>
880 with NKSP.
881 </p>
882 <code>
883 while (??condition??)
884
885 ??statements??
886
887 end while
888 </code>
889 <p>
890 A while loop is entered if the provided <code>??condition??</code>
891 expression evaluates to <i>true</i> and will then continue to execute
892 the given list of <code>??statements??</code> down to the end of the statements
893 list. The <code>??condition??</code> is re-evaluated each time execution
894 reached the end of the <code>??statements??</code> list and according to
895 that latest evaluated <code>??condition??</code> value at that point, it
896 will or will not repeat executing the statements again. If the condition
897 turned <i>false</i> instead, it will leave the loop and continue executing
898 statements that follow after the while loop block.
899 </p>
900 <p>
901 The next example will print the same message three times in a row to the
902 terminal, right after the script had been loaded by the sampler.
903 </p>
904 <code>
905 on init
906 declare $i := 3
907
908 while ($i)
909 message("Print this three times.")
910 $i := $i - 1
911 end while
912 end on
913 </code>
914 <p>
915 When the while loop is reached for the first time in this example, the
916 condition value is <code>3</code>. And as we learned before, all integer
917 values that are not <code>0</code> are interpreted as being a <i>true</i> condition.
918 Accordingly the while loop is entered, the message is printed to the
919 terminal and the variable <code>$i</code> is reduced by one. We reached
920 the end of the loop's statements list, so it is now re-evaluating the
921 condition, which is now the value <code>2</code> and thus the loop
922 instructions are executed again. That is repeated until the loop was
923 executed for the third time. The variable <code>$i</code> is now
924 <code>0</code>, so the loop condition turned finally to <i>false</i> and the
925 loop is thus left at that point and the text message was printed
926 three times in total.
927 </p>
928
929 <h2>Operators</h2>
930 <p>
931 A programming language provides so called <i>operators</i> to perform
932 certain kinds of transformations of data placed next to the operators.
933 These are the operators available with NKSP.
934 </p>
935
936 <h3>Arithmetic Operators</h3>
937 <p>
938 These are the most basic mathematical operators, which allow to add,
939 subtract, multiply and divide integer values with each other.
940 </p>
941 <code>
942 on init
943 message("4 + 3 is " & 4 + 3) { Add }
944 message("4 - 3 is " & 4 - 3) { Subtract }
945 message("4 * 3 is " & 4 * 3) { Multiply }
946 message("35 / 5 is " & 35 / 5) { Divide }
947 message("35 mod 5 is " & 35 mod 5) { Remainder of Division ("modulo") }
948 end on
949 </code>
950 <p>
951 You may either use direct integer literal numbers like used in the upper
952 example, or you can use integer number variables or integer array variables.
953 </p>
954
955 <h3>Boolean Operators</h3>
956 <p>
957 To perform logical transformations of <i>boolean</i> data, you may use the
958 following boolean operators:
959 </p>
960 <code>
961 on init
962 message("1 and 1 is " & 1 and 1) { logical "and" }
963 message("1 and 0 is " & 1 and 0) { logical "and" }
964 message("1 or 1 is " & 1 or 1) { logical "or" }
965 message("1 or 0 is " & 1 or 0) { logical "or" }
966 message("not 1 is " & not 1) { logical "not" }
967 message("not 0 is " & not 0) { logical "not" }
968 end on
969 </code>
970 <p>
971 Remember that with boolean operations, all integer values other than <code>0</code>
972 are interpreted as boolean <i>true</i> while an integer value of
973 precisely <code>0</code> is interpreted of being boolean <i>false</i>.
974 </p>
975
976 <h3>Comparison Operators</h3>
977 <p>
978 For branches in your program flow, it is often required to compare data
979 with each other. This is done by using comparison operators, enumerated
980 below.
981 </p>
982 <code>
983 on init
984 message("Relation 3 < 4 -> " & 3 < 4) { "smaller than" comparison }
985 message("Relation 3 > 4 -> " & 3 > 4) { "greater than" comparison }
986 message("Relation 3 <= 4 -> " & 3 <= 4) { "smaller or equal than" comparison}
987 message("Relation 3 >= 4 -> " & 3 >= 4) { "greater or equal than" comparison}
988 message("Relation 3 # 4 -> " & 3 # 4) { "not equal to" comparison}
989 message("Relation 3 = 4 -> " & 3 = 4) { "is equal to" comparison}
990 end on
991 </code>
992 <p>
993 All these operations yield in a <i>boolean</i> result which could then
994 by used i.e. with <code>if</code> or <code>while</code> loop statements.
995 </p>
996
997 <h3>String Operators</h3>
998 <p>
999 Last but not least, there is exactly one operator for text string data;
1000 the string concatenation operator <code>&</code>, which
1001 combines two text strings with each other.
1002 </p>
1003 <code>
1004 on init
1005 declare @s := "foo" & " bar"
1006 message(@s)
1007 end on
1008 </code>
1009 <p>
1010 We have used it now frequently in various examples before.
1011 </p>
1012
1013 <h2>Preprocessor Statements</h2>
1014 <p>
1015 Similar to low-level programming languages like C, C++, Objective C
1016 and the like, NKSP supports a set of so called preprocessor statements.
1017 These are essentially "instructions" which are "executed" or rather
1018 processed, before (and only before) the script is executed by the sampler,
1019 and even before the script is parsed by the actual NKSP language parser.
1020 You can think of a preprocessor as a very primitive parser, which is the
1021 first one getting in touch with your script, it modifies the script code
1022 if requested by your preprocessor statements in the script, and then
1023 passes the (probably) modified script to the actual NKSP language parser.
1024 </p>
1025 <p>
1026 When we discussed <a href="#comments">comments</a> in NKSP scripts before,
1027 it was suggested that you might comment out certain code parts to disable
1028 them for a while during development of scripts. It was also suggested
1029 during this language tour that you should not use string variables or use
1030 the <code>message()</code> function with your final production sounds.
1031 However those are very handy things during development of your instrument
1032 scripts. You might even have a bunch of additional code in your scripts
1033 which only satisfies the purpose to make debugging of your scripts more easy,
1034 which however wastes on the other hand precious CPU time. So what do you
1035 do? Like suggested, you could comment out the respective code sections as
1036 soon as development of your script is completed. But then one day you
1037 might continue to improve your scripts, and the debugging code would be
1038 handy, so you would uncomment all the relevant code sections to get them
1039 back. When you think about this, that might be quite some work each time.
1040 Fortunately there is an alternative by using preprocessor statements.
1041 </p>
1042
1043 <h3>Set a Condition</h3>
1044 <p>
1045 First you need to set a preprocessor condition in your script. You can do
1046 that like this:
1047 </p>
1048 <code>
1049 SET_CONDITION(??condition-name??)
1050 </code>
1051 <p>
1052 This preprocessor "condition" is just like some kind of
1053 <i title="A variable which can only have two states: i.e. true or false.">
1054 boolean variable
1055 </i>
1056 which is only available to the preprocessor and by using
1057 <code>SET_CONDITION(??condition-name??)</code>, this is like setting this
1058 preprocessor condition to <i>true</i>. Like with regular script
1059 variables, a preprocessor condition name can be chosen quite arbitrarily
1060 by you. But again, there are some pre-defined preprocessor conditions
1061 defined by the sampler for you. So you can only set a condition name here
1062 which is not already reserved by a built-in preprocessor condition. Also
1063 you shall not set a condition in your script again if you have already set it
1064 before somewhere in your script. The NKSP preprocessor will ignore setting
1065 a condition a 2nd time and will just print a warning when the script is
1066 loaded, but you should take care of it, because it might be a cause for
1067 some bug.
1068 </p>
1069
1070 <h3>Reset a Condition</h3>
1071 <p>
1072 To clear a condition in your script, you might reset the condition like so:
1073 </p>
1074 <code>
1075 RESET_CONDITION(??condition-name??)
1076 </code>
1077 <p>
1078 This is like setting that preprocessor condition back to <i>false</i> again.
1079 You should only reset a preprocessor condition that way if you did set it
1080 with <code>SET_CONDITION(??condition-name??)</code> before. Trying to
1081 reset a condition that has not been set before, or trying to reset a
1082 condition that has already been reset, will both be ignored by the samlper,
1083 but again you will get a warning, and you should take care about it.
1084 </p>
1085
1086 <h3>Conditionally Using Code</h3>
1087 <p>
1088 Now what do you actually do with such preprocessor conditions? You can use
1089 them for the NKSP language parser to either
1090 </p>
1091 <ul>
1092 <li>use certain parts of your code</i>
1093 <li><b>and</b> / <b>or</b> to ignore certain parts of your code</i>
1094 </ul>
1095 <p>
1096 You can achieve that by wrapping NKSP code parts into a pair of either
1097 </p>
1098 <code>
1099 USE_CODE_IF(??condition-name??)
1100
1101 ??some-NKSP-code-goes-here??
1102
1103 END_USE_CODE
1104 </code>
1105 <p>
1106 preprocessor statements, or between
1107 </p>
1108 <code>
1109 USE_CODE_IF_NOT(??condition-name??)
1110
1111 ??some-NKSP-code-goes-here??
1112
1113 END_USE_CODE
1114 </code>
1115 <p>
1116 statements. In the first case, the NKSP code portion is used by the NKSP
1117 language parser if the given preprocessor <code>??condition-name??</code> is set
1118 (that is if condition is <i>true</i>).
1119 If the condition is not set, the NKSP code portion in between is
1120 completely ignored by the NKSP language parser.
1121 </p>
1122 <p>
1123 In the second case, the NKSP code portion is used by the NKSP
1124 language parser if the given preprocessor <code>??condition-name??</code> is <b>not</b> set
1125 (or was reset)
1126 (that is if condition is <i>false</i>).
1127 If the condition is set, the NKSP code portion in between is
1128 completely ignored by the NKSP language parser.
1129 </p>
1130 <p>
1131 Let's look at an example how to use that to define conditional debugging
1132 code.
1133 </p>
1134 <code>
1135 SET_CONDITION(DEBUG_MODE)
1136
1137 on init
1138 declare const %primes[12] := ( 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37 )
1139 declare $i
1140
1141 USE_CODE_IF(DEBUG_MODE)
1142 message("This script has just been loaded.")
1143
1144 $i := 0
1145 while ($i < num_elements(%primes))
1146 message("Prime " & $i & " is " & %primes[$i])
1147 $i := $i + 1
1148 end while
1149 END_USE_CODE
1150 end on
1151
1152 on note
1153 USE_CODE_IF(DEBUG_MODE)
1154 message("Note " & $EVENT_NOTE & " was triggered with velocity " & $EVENT_VELOCITY)
1155 END_USE_CODE
1156 end on
1157
1158 on release
1159 USE_CODE_IF(DEBUG_MODE)
1160 message("Note " & $EVENT_NOTE & " was released with release velocity " & $EVENT_VELOCITY)
1161 END_USE_CODE
1162 end on
1163
1164 on controller
1165 USE_CODE_IF(DEBUG_MODE)
1166 message("MIDI Controller " & $CC_NUM " changed its value to " & %CC[$CC_NUM])
1167 END_USE_CODE
1168 end on
1169 </code>
1170 <p>
1171 The <i>built-in function</i> <code>num_elements()</code> used above, can
1172 be called to obtain the size of an array variable at runtime.
1173 As this script looks now, the debug messages will be printed out. However
1174 it requires you to just remove the first line, or to comment out the first
1175 line, in order to disable all debug code portions in just a second:
1176 </p>
1177 <code>
1178 { Setting the condition is commented out, so our DEBUG_MODE is disabled now. }
1179 { SET_CONDITION(DEBUG_MODE) }
1180
1181 on init
1182 declare const %primes[12] := ( 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37 )
1183 declare $i
1184
1185 USE_CODE_IF(DEBUG_MODE) { Condition is not set, so this entire block will be ignored now. }
1186 message("This script has just been loaded.")
1187
1188 $i := 0
1189 while ($i < num_elements(%primes))
1190 message("Prime " & $i & " is " & %primes[$i])
1191 $i := $i + 1
1192 end while
1193 END_USE_CODE
1194 end on
1195
1196 on note
1197 USE_CODE_IF(DEBUG_MODE) { Condition is not set, no message will be printed. }
1198 message("Note " & $EVENT_NOTE & " was triggered with velocity " & $EVENT_VELOCITY)
1199 END_USE_CODE
1200 end on
1201
1202 on release
1203 USE_CODE_IF(DEBUG_MODE) { Condition is not set, no message will be printed. }
1204 message("Note " & $EVENT_NOTE & " was released with release velocity " & $EVENT_VELOCITY)
1205 END_USE_CODE
1206 end on
1207
1208 on controller
1209 USE_CODE_IF(DEBUG_MODE) { Condition is not set, no message will be printed. }
1210 message("MIDI Controller " & $CC_NUM " changed its value to " & %CC[$CC_NUM])
1211 END_USE_CODE
1212 end on
1213 </code>
1214 <p>
1215 Now you might say, you could also achieve that by declaring and using
1216 a regular NKSP variable. That's correct, but there are two major
1217 advantages by using preprocessor statements.
1218 </p>
1219 <ol>
1220 <li>
1221 <b>Saving Resources</b> -
1222 The preprocessor conditions are only processed before the script is
1223 loaded into the NKSP parser. So in contrast to using NKSP variables,
1224 the preprocessor solution does not waste any CPU time or memory
1225 resources while executing the script. That also means that variable
1226 declarations can be disabled with the preprocessor this way
1227 and thus will also safe resources.
1228 </li>
1229 <li>
1230 <b>Cross Platform Support</b> -
1231 Since the code portions filtered out by the preprocessor never make it
1232 into the NKSP language parser, those filtered code portions might also
1233 contain code which would have lead to parser errors. For example you
1234 could use a built-in preprocessor condition to check whether your script
1235 was loaded into LinuxSampler or rather into another sampler. That way
1236 you could maintain one script for both platforms: NKSP and KSP.
1237 Accordingly you could
1238 also check a built-in variable to obtain the version of the sampler in
1239 order to enable or disable code portions of your script that might
1240 use some newer script features of the sampler which don't exist in older
1241 version of the sampler.
1242 </li>
1243 </ol>
1244 <p>
1245 As a rule of thumb: if there are things that you could move from your
1246 NKSP executed programming code out to the preprocessor, then you should
1247 use the preprocessor instead for such things. And like stated above,
1248 there are certain things which you can only achieve with the preprocessor.
1249 </p>
1250
1251 <h2>What Next?</h2>
1252 <p>
1253 You have completed the introduction of the NKSP real-time instrument
1254 script language at this point. You can now dive into the details of the
1255 NKSP language by moving on to the
1256 <a href="nksp_reference.html">NKSP reference documentation</a>.
1257 Which provides you an overview and quick access to the details of all
1258 built-in functions, built-in variables and more.
1259 </p>
1260
1261 </body>
1262 </html>

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