| definition: |
(!?) :: [a] -> Int -> Maybe a
[] !? _ = Nothing
(x:xs) !? i | i > 0 = xs !? (i-1)
| i == 0 = Just x
| otherwise = Nothing
|
| demand: |
argument 1 |
| deterministic: |
deterministic operation |
| documentation: |
Get index of a list and return it, if it exists. Return Nothing if not. |
| failfree: |
(_, _) |
| indeterministic: |
referentially transparent operation |
| infix: |
no fixity defined |
| iotype: |
{({[]},_) |-> {Nothing} || ({:},_) |-> {Just,Nothing}}
|
| name: |
!? |
| precedence: |
no precedence defined |
| result-values: |
{Just,Nothing}
|
| signature: |
[a] -> Prelude.Int -> Prelude.Maybe a |
| solution-complete: |
operation might suspend on free variables |
| terminating: |
possibly non-terminating |
| totally-defined: |
possibly non-reducible on same data term |