Constraints

Extension

Constraints let you specify conditions in an OOP fashion. You can perform logical operations on the constraint object itself to further filter or refine your query.( // Create a constraint. c = Constraint({ arg obj; obj.even }) and: Constraint({ arg obj; obj % 4 == 0 }) and: (Constraint({ arg obj; obj == 8 }).not); )

c is now a constraint object that can be used to validate that an input is even, divisible by 4 and is not the number 8.c.value(3) c.value(8) c.value(4) c.value(12)

This can be used any place a function that returns true/false is required. eg. select, reject, every, any( // run numbers through it 50.do({ n = 40.rand; [n,c.value(n)].postln }); )

It can be used in place of a function for SequenceableCollections, Streams and Patterns( // filter a collection Array.fill(100,{ 100.rand }) .select(c) // acts like a function .do({ arg num; num.postln; }); ) ( // Use to filter a Pattern p = Pseries(0,1,100) .select(c); ) // Unfiltered Pseries(0,1,100).asStream.all.do({arg num; num.postln;}) // Filtered p.asStream.all.do({ arg num; num.postln }); ( // and here is everybody that gets rejected by the constraint p = Pseries(0,1,100) .reject(c); ) p.asStream.all.do({ arg num; num.postln });

The below example is expressed using only Constraint.( c = Constraint({ arg obj; obj.even }) and: Constraint({ arg obj; obj % 4 == 0 }) and: (Constraint({ arg obj; obj == 8 }).not); )

It could also be expressed this way( c = IsEven.new and: Constraint({ arg obj; obj % 4 == 0 }) and: Constraint({ arg obj; obj != 8 }); )

Constraints respond to

.not .or(aConstraint) .and(aConstraint) .xor(aConstraint) .reject(aConstraint) .select(aConstraint)

by returning a new compound constraint that expresses that logic.( c = IsEven.new; d = Constraint({ arg num; num == 3 }); e = c or: d; // if its even or it is the number 3 ) ( c = IsEven.new; d = Constraint({ arg num; num == 4 }); e = c.reject(d); // if its even and also reject it if it is the number 4 )