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class::Symbol
summary::a unique name for something
categories::Core
description::
A symbol, like a link::Classes/String::, is a sequence of characters. Unlike strings, two symbols
with exactly the same characters will be the exact same object. Symbols are optimized for recreating
the same symbol over and over again. In practice, this means that symbols are best used for
identifiers or tags that are only meaningful within your program, whereas you should use a string
when your characters are really processed as text data. Use symbols to name things, use strings for
input and output.
Good uses of symbols include symbolic constant values and link::Classes/Dictionary:: keys.
Symbols are represented syntactically as literals which are described in link::Reference/Literals#Symbols::.
subsection::Creating a Symbol
A symbol can be written by surrounding characters by single quotes (may include whitespace):
code::'foo bar'::
Or by a preceding backslash (then it may not include whitespace):
code::\foo::
A String can be converted into a symbol:
code::"arbeit".scramble.asSymbol;::
classmethods::
private::new
instancemethods::
subsection::Testing
method::isClassName
Answer whether the symbol can be a class name. This does not say if the class exists.
code::
\Array.isClassName;
\Bauxite.isClassName;
::
method::isMetaClassName
Answer whether the symbol can be meta class name. This does not say if the class exists.
code::
\Meta_Array.isMetaClassName;
::
method::isSetter
Answer whether the symbol has a trailing underscore.
code::
'action_'.isSetter;
::
method::isPrimitiveName
Answer whether the symbol is a valid primitive name
code::
'_SymbolIsClassName'.isPrimitiveName;
::
method::isPrefix
Answer whether the symbol is a prefix of another one
code::
'a'.isPrefix('all'); // true
'z'.isPrefix('all'); // false
::
method::isIdentifier
Return true if the symbol is a valid variable name, or equivalently a valid method name in the two
most common method call syntaxes (code::foo.bar():: and code::bar(foo)::). A valid identifier
contains only alphanumeric characters and underscores, and the first character must be a lowercase
letter.
method::isBinaryOp
Return true if the symbol is a valid binary operator. A valid binary operator contains only the
symbols code::!@%&*-+=|<>?/::, does not start with 'code:://::' or 'code::/*::', and is not the
string 'code::=::'.
subsection::Conversion
method::asString
Convert to a String
method::asInteger
Convert to an Integer
method::asClass
Answer the Class named by the receiver.
method::asSetter
Return a symbol with a trailing underscore added.
method::asGetter
Return a symbol with a trailing underscore removed.
method::ascii
return the ascii codes as an array
method::asSpec
Convert to a ControlSpec
method::asTuning
Convert to a Tuning
method::asScale
Convert to a Scale
subsection::Environments
Symbols are used as keys to look up objects in dictionaries and environments, but also in arrays.
See link::Classes/IdentityDictionary::, link::Classes/Environment::, link::Classes/Event::
code::
a = ();
a.put(\commune, 1871);
a.at(\commune);
::
method::envirPut
put a value to the current environment using receiver as key
method::envirGet
return a value from the current environment using receiver as key
discussion::
code::
\foo.envirPut(100);
\foo.envirGet;
\foo.envirPut(nil);
::
subsection::Math
Symbols respond to all unary and binary math operations by returning themselves. The result of any math operation between a Number or other math object and a Symbol is to return the Symbol. This allows for example operations on lists of notes which contain 'rest's to preserve the rests.
code::Pseq([1, 3, \rest, 2, 4] + 8);::
method::applyTo
Use the symbol as a method selector and perform the message on firstArg, with args as arguments. This is used for mixing functions with method selectors (see also: Function).
discussion::
code::
'%'.applyTo(2553, 345);
['+', '-', '*', { |a, b| a.rand + b.rand } ].choose.applyTo(2, 3);
::
subsection::Synthesis
Inside SynthDefs and UGen functions, symbols can be used to conveniently specify control inputs of different rates and with lags (see: NamedControl, ControlName, and Control).
method::kr
Return a control rate NamedControl input with a default value (val), and if supplied, with a lag. If val is an array, the control will be multichannel.
A link::Classes/ControlSpec:: provided to the code::spec:: parameter will be written into the spec metadata for the current synth.
discussion::
code::
a = { SinOsc.ar(\freq.kr(440, 1.2)) }.play;
a.set(\freq, 330);
a.release;
a = { SinOsc.ar(\freq.kr([440, 460], 1.2)) }.play;
a.setn(\freq, [330, 367]);
a.release;
::
method::ar
Return an audio rate NamedControl input with a default value (val), and if supplied, with a lag. If val is an array, the control will be multichannel.
method::ir
Return an initialization rate NamedControl input with a default value (val). If val is an array, the control will be multichannel.
method::tr
Return a TrigControl input with a default value (val). If val is an array, the control will be multichannel.
discussion::
code::
a = { Ringz.ar(T2A.ar(\trig.tr), \freq.kr(500, 1), 0.8) }.play;
a.set(\freq, 330, \trig, 1);
a.set(\freq, 830, \trig, 1);
a.release;
::
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