select(Thing,Function) -- select elements from an object with an iterator

Synopsis

Function: select
Usage:

select(x, f)
Inputs:
- x, a thing, an instance of a class with the iterator method installed;
- f, a function, returning either true or false;
Outputs:
- an iterator,

Description

Suppose x is an instance of a class with the iterator method installed, e.g., a string, and suppose iter is the output of iterator x. Then a new Iterator object is returned whose next method returns the next output of next iter for which f next iter is true, unless next iter returns StopIteration, in which case this new iterator does the same.

i1 : selectiter = select("foo", i -> i == "o")

o1 = iterator "foo"

o1 : Iterator

i2 : next selectiter

o2 = o

i3 : next selectiter

o3 = o

i4 : next selectiter

o4 = StopIteration

o4 : Symbol

Ways to use this method: