Bool elem(a val, [a] list, Bool(a, a) eq=equal)
Arguments
val: The value to search for ("needle")list: The list to search ("haystack")eq: Optionally, the function used to check for presence (the default is Builtins::equal, obviously, but Builtins::identical might be used)
Usage
Check whether the "needle" occurs at least once in the "haystack". This function can be thought of as a specialised version of any
