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Reference · stzList

ItemsAtPositions()

FindW: the extended (expressive) where-scan. Returns the matching -- POSITIONS (use ItemsW for the items at those positions). It accepts -- @NextItem/@PreviousItem/... and the Q(EXPR).Method(...) predicate form. -- ItemsAtPositions: get items at given positions

also written: ItemsAt

Basic examples (2)

Softanza
aOrders = [ "tea", "rice", "tea", "fish", "rice", "tea", "soup", "tea", "rice" ]
? @@( StzListQ([ 1, 2, 3, 4, 5, 6, 7, 8, 9 ]).FindW("@item % 3 = 1") )
? @@( StzListQ(aOrders).ItemsAtPositions([ 1, 4, 7 ]) )
Output
[ 1, 4, 7 ]
[ "tea", "fish", "soup" ]

run on 2026-10-02 04:24 inside the library at commit 0e72e2e2c; taken from 06-walk-ask-produce-act.en.md(opens in a new tab)

Softanza
o1 = new stzList([ "a", "ab", "b", 1:3, "a", "ab", "abc", "b", "bc", 1:3,"c" ])
? o1.FindDuplicates()
? @@( o1.ItemsAtPositions( o1.FindDuplicates() ) )
? @@( o1.Duplicates() ) + NL
? @@( o1.DuplicatesZ() )
Output
5
6
8
10

[ "a", "ab", "b", [ 1, 2, 3 ] ]
[ "a", "ab", "b", [ 1, 2, 3 ] ]

[ [ "a", [ 5 ] ], [ "ab", [ 6 ] ], [ "b", [ 8 ] ], [ [ 1, 2, 3 ], [ 10 ] ] ]

run on 2026-10-02 04:22 inside the library at commit 0e72e2e2c; taken from 266_findduplicates.ring(opens in a new tab)

The extensions of this method

Each extension, and whether it exists for this method; an extension that exists combines with the others (FindSTCS).

Extension
Exists
What it adds · The names
Q
yes
does what the method does, then returns the object, so the call can be chained · ItemsAtPositionsQ
QQ
no
chains on the next, more specific type of object (the Q ladder)
QQQ
no
chains on the most specific type of object (the Q ladder)
QRT
no
returns the result as an object of the requested type
CS
no
takes a case-sensitivity flag
ST
no
takes the position to start from (StartingAt)
IB
no
takes bounds that are included (IncludingBounds)
XT
no
the extended form: more parameters than the base method
XTT
no
yet another extension: a further extended form, after XT
Z
no
includes the position in what it returns
ZZ
no
returns positions as sections, [start, end]
W
no
selects by a condition
WF
no
selects by a condition, with the expressive keywords (@NextItem, @PreviousItem...)
D
no
takes a direction, forward or backward (Directional)
F
no
takes a function (the condition or the update is given as a function); the forms document also uses F for the future form, which defers the action
Many
no
works on a collection of items instead of one (the plural form)
Except
no
takes exceptions, what to leave out (the exceptional form)
U
no
returns the result without duplication

Every example is a test file of the library, run inside the library for this page; only those whose output kept every promise their file wrote are shown.

See also