iterator -- get an iterator

Description

An iterator is an object that is used to traverse through x. Usually, but not necessarily, this will be an instance of the Iterator class.

i1 : iter = iterator {1, 2, 3}

o1 = iter

o1 : Iterator

The class of an iterator should have a next method installed that gets the next element of x.

i2 : next iter

o2 = 1

i3 : next iter

o3 = 2

i4 : next iter

o4 = 3

If x contains only a finite number of elements, then next should return the symbol StopIteration after exhausting them all.

i5 : next iter

o5 = StopIteration

o5 : Symbol

Instances of classes with this method installed can be used like lists in for loops and scan.

i6 : lookup(iterator, String)

o6 = FunctionClosure[../../../../Macaulay2/m2/iterators.m2:20:24-27:16]

o6 : FunctionClosure

i7 : for i in "foo" list i

o7 = {f, o, o}

o7 : List

i8 : scan("foo", print)
f
o
o

They can also be passed to apply and select. In each case, an Iterator object will be returned that is an iterator for itself.

i9 : apply("foo", toUpper)

o9 = (F, O, O)

o9 : Sequence

i10 : for i in oo list i

o10 = {F, O, O}

o10 : List

i11 : select("foo", i -> i == "o")

o11 = iterator "foo"

o11 : Iterator

i12 : for i in oo list i

o12 = {o, o}

o12 : List

The source of this document is in Macaulay2Doc/doc_iterators.m2:106:0.