Modern Array IndexOf

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IndexOf

Returns the index of the first element equal to a value, or -1 if there is none.

Syntax

IndexOf( a, v ) as int32

Notes

• Requires = on T. It is a free procedure rather than a member so that requirement lands on the call site: every member body of a generic is instantiated whether or not it is called, so as a member it would make Array( of T ) unusable for any T without =.
• Returns -1 when the value is absent, which is why the result is signed. Use Contains when the position is not wanted.
• T is inferred from the array, so the value must already be a T -- IndexOf( nums, 3 ) against an Array( of int32 ) is error 340, because a bare 3 is an integer.
• O(n), comparing from index 0 upward.

Examples

#import "std/containers"
using containers

'' A free procedure, not a member: it needs '=' on T, and as a member that
'' requirement would fall on every instantiation of Array whether or not it
'' was ever called
dim v as Array( of string )
v.Push( "ada" ) : v.Push( "grace" )

print IndexOf( v, "grace" )      '' 1
print IndexOf( v, "alan" )       '' -1 -- absent, which is why it is signed

dim as string wanted = "ada"
if IndexOf( v, wanted ) >= 0 then print "present"

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Library: Array Container
Category: Array
Documented under: Members