ChucK : Language Specification > Overview

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Overview

ChucK is a strongly-typed, strongly-timed, concurrent audio and multimedia programming language. It is compiled into virtual instructions, which is immediately run in the ChucK Virtual Machine.
This guide documents the features of the Language, Compiler, and Virtual Machine for a ChucK programmer.

Running ChucK

Some quick notes on running ChucK. Please see VM options for a more complete guide to the command line options).

To run ChucK with a chuck-program/patch called foo.ck :

% chuck foo.ck

To run ChucK with multiple patches concurrently (or the same one multiple times):

% chuck foo.ck bar.ck bar.ck boo.ck

There are several flags you can specify to control how ChucK operates, or to find out about the system. For example, the following will probe the audio system on your computer and print out all available audio and MIDI devices. You may then refer to them (by number usually) from the command line or from your program. (see VM Options for a complete list)

% chuck --probe

ChucK can be run in a different terminal as a host/listener that patches may be sent to. The server should invoke the --loop flag to specify that the virtual machine should not halt automatically (when the current programs exit).

% chuck --loop

If a ChucK listener is running, we can (from a second terminal) send a program/patch to to the listener by using the + command line option:

% chuck + foo.ck

Similarly, you can use - and = to remove/replace a patch in the listener, and use ^ to find out the status.

See the guide to On-the-fly Programming for more information.

To run most of the code or examples in this language specification, you only need to use the basic chuck program.

Chuck Program Syntax and Structure

Comments

Comments are sections of code that are ignored by a compiler. These help other programmers (and yourself) interpret your code. Double slashes indicate to the compiler to skip the rest of the line. /* and */ denotes block commenting - the compiler ignores the text in between.
(Note: block comments cannot be nested)

// this is a comment
int foo; // another comment

/* 
    this is a block comment
    still going...
*/

Debug Print

For the time being, stdout and chout have been temporarily disabled for the present release. In their place we have provided a debug print syntax:

// prints out value of _expression_
<<< expression >>>;

This will print the values and types of any expressions placed within them. This debug print construction may be placed around any non-declaration expression (non l-value) and will not affect the execution of the code. Expressions which represent an object will print the value of that object's reference address:

// assign 5 to a newly declared variable
5 => int i;
// prints "5 : (int)"
<<<i>>>;

// prints "hello! : (string)"
<<<"hello!">>>; //prints "hello! : (string)"

// prints "3.5 : (float)"
<<<1.0 + 2.5>>> => float x;

For more formatted data output, a comma-separated list of expressions will print only their respective values (with one space between):

// prints "the value of x is 3.5" (x from above)
<<<"the value of x is", x>>>;

// prints "4 + 5 is 9"
<<<"4 + 5 is", 4 + 5>>>;

// prints "here are 3 random numbers ? ? ?"
<<<"here are 3 random numbers", 
    Std.rand2(0,9), 
    Std.rand2(0,9),
    Std.rand2(0,9) >>>;

Reserved Words

Like any programming language, ChucK reserves certain words and character sequences. These have special meanings.

primitive types

control structures

class keywords

other chuck keywords

special values

special durations

special global ugens

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