Pwhile while a condition holds,  repeatedly embed  stream

superclass: FuncFilterPattern

Pwhile(func, pattern)

(

z = true;

a = Pwhile({ z }, Pseq(#[1, 2, 3]));

x = a.asStream;

);

7.do({ x.next.postln; }); // while z == true, the values are embedded

z = false; // set z to false

x.next; // the rest of the stream is still embedded

x.next;

x.next; // but then it is not continued.

x.next;

x.next;

x.next;