lib.lists.findSingle

Find the sole element in the list matching the specified predicate.

Returns default if no such element exists, or multiple if there are multiple matching elements.

Inputs

pred

Predicate

default

Default value to return if element was not found.

multiple

Default value to return if more than one element was found

list

Input list

Type

findSingle :: (a -> Bool) -> a -> a -> [a] -> a

Examples

findSingle (x: x == 3) "none" "multiple" [ 1 3 3 ]
=> "multiple"
findSingle (x: x == 3) "none" "multiple" [ 1 3 ]
=> 3
findSingle (x: x == 3) "none" "multiple" [ 1 9 ]
=> "none"

Noogle detected

• lib.findSingle

findSingle =
    pred: default: multiple: list:
    let
      found = filter pred list;
      len = length found;
    in
    if len == 0 then
      default
    else if len != 1 then
      multiple
    else
      head found;