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.\" Copyright (c) 2025 Bruce Hill
.\" All rights reserved.
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.TH List.where 3 2025-04-30 "Tomo man-pages"
.SH NAME
List.where \- find an index where a predicate matches
.SH LIBRARY
Tomo Standard Library
.SH SYNOPSIS
.nf
.BI List.where\ :\ func(list:\ [T],\ predicate:\ func(item:&T\ ->\ Bool)\ ->\ Int)
.fi
.SH DESCRIPTION
Find the index of the first item that matches a predicate function (if any).


.SH ARGUMENTS

.TS
allbox;
lb lb lbx lb
l l l l.
Name	Type	Description	Default
list	[T]	The list to search through. 	-
predicate	func(item:&T -> Bool)	A function that returns `yes` if the item's index should be returned or `no` if it should not. 	-
.TE
.SH RETURN
Returns the index of the first item where the predicate is true or `none` if no item matches.

.SH EXAMPLES
.EX
>> [4, 5, 6].where(func(i:&Int): i.is_prime())
= 5 : Int?
>> [4, 6, 8].find(func(i:&Int): i.is_prime())
= none : Int?
.EE