2.6 The COMMON-EXTENSIONS module
position
Open generic function
Summary
Returns the key at which a particular value occurs in a sequence.
Signature
position sequence value #key predicate skip => key
Arguments
- sequence
- An instance of
<sequence>. - value
- An instance of
<object>. - predicate
- An instance of
<function>. Default value:\==. - skip
- An instance of
<integer>. Default value: 0.
Values
- key
- An instance of
<object>.
Library
common-extensions
Module
common-extensions
Description
Returns the key at which value occurs in sequence.
If predicate is supplied, position uses it as an equivalence predicate for comparing sequence's elements to value. It should take two objects and return a boolean. The default predicate used is \==.
The skip argument is interpreted as it is by Dylan's find-key function: position ignores the first skip elements that match value, and if skip or fewer elements satisfy predicate, it returns #f.