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Reference · stzList

NumberOfDuplicates()

NumberOfDuplicates counts the duplicate OCCURRENCES (every 2nd+ appearance), not the number of distinct duplicated items. For [ "A","B","2","A","A","B",2,2,"." ] that is 4 (A twice, B once, 2 once). NumberOfDuplicatedItems (distinct) would be 3.

also written: HowManyDuplicates · NumberOfDuplications

Basic examples (2)

Softanza
oW = new stzList( o1.Words() )
? oW.ContainsDuplicates()
? oW.NumberOfDuplicates()
Output
1
3

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

Softanza
o1 = new stzList([ "*", "4", "*", "3", "4" ])
? o1.NumberOfDuplicates() + NL
? o1.Duplicates()
Output
2

*
4

run on 2026-10-02 04:22 inside the library at commit 0e72e2e2c; taken from 260_numberofduplicates.ring(opens in a new tab)

Scope (3)

Softanza
o1 = new stzList([ 5, 7, 5, 5, 4, 7 ])
? o1.ContainsDuplicates()
? o1.HowManyDuplicates()
? @@( o1.FindDuplicates() )
? @@( o1.DuplicatesZ() ) # Or DuplicatesAndTheirPositions()
o1.RemoveDuplicates()
? @@( o1.Content() )
Output
1
3
[ 3, 4, 6 ]
[ [ 5, [ 3, 4 ] ], [ 7, [ 6 ] ] ]
[ 5, 7, 4 ]

run on 2026-10-02 04:22 inside the library at commit 0e72e2e2c; taken from 243_containsduplicates.ring(opens in a new tab)

Softanza
o1 = new stzList([ "tunis", 1:3, 1:3, "gafsa", "tunis", "tunis", 1:3, "gabes", "tunis", "regueb", "regueb" ])
o1.Reverse()
? @@( o1.Content() ) + NL
? o1.NumberOfDuplicates()
? o1.NumberOfDuplicatesOf("tunis") + NL	# Or NumberOfOccurrence("tunis")
? @@( o1.DuplicatedItems() ) + NL
? @@( o1.DuplicatesRemoved() )
Output
[ "regueb", "regueb", "tunis", "gabes", [ 1, 2, 3 ], "tunis", "tunis", "gafsa", [ 1, 2, 3 ], [ 1, 2, 3 ], "tunis" ]

6
4

[ "regueb", "tunis", [ 1, 2, 3 ] ]

[ "regueb", "tunis", "gabes", [ 1, 2, 3 ], "gafsa" ]

run on 2026-10-02 04:23 inside the library at commit 0e72e2e2c; taken from 588_reverse.ring(opens in a new tab)

Softanza
o1 = new stzList([
		"*", "*4", "*4*", "*4*3", "*4*34",
		"4", "4*", "4*3", "4*34", "*", "*3",
		"*34", "3", "34", "4"
	])
# numberofduplicates example 1
? @@( o1.NumberOfDuplicates() )
# numberofduplicates example 2
? @@( o1.FindDuplicates() )
# numberofduplicates example 3
? @@( o1.Duplicates() )
# numberofduplicates example 4
? @@( o1.DuplicatesZ() )
Output
2
[ 10, 15 ]
[ "*", "4" ]
[ [ "*", [ 10 ] ], [ "4", [ 15 ] ] ]

run on 2026-10-02 04:22 inside the library at commit 0e72e2e2c; taken from 167_numberofduplicates.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
no
does what the method does, then returns the object, so the call can be chained
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
yes
takes a case-sensitivity flag · NumberOfDuplicatesCS
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