Head-strict
<theory> A head-strict function will not necessarily evaluate every
cons cell of its (list) argument, but whenever it does evaluate a cons cell it will also evaluate the element in the head of that cell.
An example of a head-strict function is
beforeZero :: [Int] -> [Int] beforeZero []
= [] beforeZero (0:xs) = [] beforeZero (x:xs) = x : beforeZero xs
which returns a list up to the first zero.
This pattern of evaluation is important because it is common in functions which operate on a list of inputs.
See also
tail-strict,
hyperstrict.
