/usr/share/axiom-20170501/src/algebra/STEP.spad is in axiom-source 20170501-3.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 | )abbrev category STEP StepThrough
++ Description:
++ A class of objects which can be 'stepped through'.
++ Repeated applications of \spadfun{nextItem} is guaranteed never to
++ return duplicate items and only return "failed" after exhausting
++ all elements of the domain.
++ This assumes that the sequence starts with \spad{init()}.
++ For infinite domains, repeated application
++ of \spadfun{nextItem} is not required to reach all possible domain elements
++ starting from any initial element.
++
++ Conditional attributes\br
++ \tab{5}infinite\tab{5}repeated nextItem's are never "failed".
StepThrough() : Category == SIG where
SIG ==> SetCategory with
init : constant -> %
++ init() chooses an initial object for stepping.
nextItem : % -> Union(%,"failed")
++ nextItem(x) returns the next item, or "failed"
++ if domain is exhausted.
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