class::Interpreter
summary:: The interpreter defines a context in which interactive commands are compiled and executed.
categories:: Core>Kernel
related::Guides/How-to-Use-the-Interpreter

description::
The interpreter is an object that handles the translation and execution of code at runtime. It is that what runs any program code and defines a context for it.

code::
(
a = 5 + 7;
this.cmdLine.postln;
)
::

classMethods::

private::new

instanceMethods::

subsection::Accessing

In the interpreter, code::this:: refers to the interpreter itself, e.g.: code::this.postln::

The interpreter defines global variables (code::a:: … code::z::), that can be used for interactive programming. Except these single letter variables ("interpreter variables"), all variables have to be defined by the keyword code::var:: (see: link::Reference/Assignment::, and link::Reference/Scope::).

code::
// typical usage
a = 4;
b = 3;
b = b + a;

// some sound
a = Synth(\default);
g = fork { loop { 0.1.wait; a.set(\freq, 200 + 20.0.rand2.postln) } };
g.stop; a.free;

// an overview of all the variables
this.inspect;
::

note::Use these variables with a bit of extra care – as they are global, they remain in memory and one piece of code may happen to interfere with another one. The variable code::s:: is by convention bound to the default server (link::Classes/Server::) and should not be changed.::



method::clearAll

set the values of the variables code::a:: through code::z:: to nil.

code::
x = 123;
x.postln;
this.clearAll;
x.postln;
::

subsection::Compile & Interpret

method::interpret

Compile and execute a link::Classes/String::.

code::
this.interpret("(123 + 4000).postln");
::

method::interpretPrint

Compile and execute a link::Classes/String::, printing the result.

code::
this.interpretPrint("123 + 4000");
::

method::compile

Compile a String and return a link::Classes/Function::.

code::
(
z = this.compile("(123 + 4000).postln");
z.postln;
z.value;
)
::

method::compileFile

Reads the file at pathName, compiles it and returns a Function.
The file must contain a valid SuperCollider expression, naturally.
This will not compile class definitions, only expressions.

method::executeFile

Reads the file at pathName, compiles it and executes it, returning the result.
The file must contain a valid SuperCollider expression, naturally.
This will not compile class definitions, only expressions.

method::cmdLine

Returns the previously interpreted code.

code::
1 + 2;
this.cmdLine
::

method::codeDump

this interpreter variable can be set to evaluate a function with any successfully compiled code.
see e.g. the class History.

code::
a = [ ]; // store all the code evaluated in a
this.codeDump = { |code| a = a.add(code) };
1 + 3;
f = { "hallo" };
a.postcs;
codeDump = nil; // reset to nil.
::

method::preProcessor

If this is set to a function, all interactively executed code is piped through it before parsing and
interpreting. This is mostly used for developing domain-specific live coding languages that piggyback
off the SuperCollider editing environment.

This function is called by link::Classes/Interpreter#-interpretPrintCmdLine:: with two arguments:
the code string and the interpreter itself.

code::
// silly but simple: understand a Saw for every SinOsc
this.preProcessor = { |code| code.replace("SinOsc", "Saw") };

{ SinOsc.ar(200) * 0.1 }.play;

preProcessor = nil; // reset to nil.
::

method::a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z

Global variables ("interpreter variables") for interactive programming (see link::#Accessing::).

method::functionCompileContext

The compiler uses this method as a virtual context in which to compile code.