Returns the key at which a particular value occurs in a 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.
open
| sequence | An instance of <sequence>. |
| value | An instance of <object>. |
| predicate: | An instance of <function>. Defaults to ==. |
| skip: | An instance of <integer>. Defaults to 0. |
| key | An instance of type-union(<integer>, <false>). |