null package:base

Test whether the structure is empty. The default implementation is Left-associative and lazy in both the initial element and the accumulator. Thus optimised for structures where the first element can be accessed in constant time. Structures where this is not the case should have a non-default implementation.

Examples

Basic usage:

>>> null []
True

>>> null [1]
False

null is expected to terminate even for infinite structures. The default implementation terminates provided the structure is bounded on the left (there is a leftmost element).

>>> null [1..]
False

Test whether a list is empty.

>>> null []
True

>>> null [1]
False

>>> null [1..]
False

The constant nullFunPtr contains a distinguished value of FunPtr that is not associated with a valid memory location.

The constant nullPtr contains a distinguished value of Ptr that is not associated with a valid memory location.

The null address.

Test whether the structure is empty.

Examples

Basic usage:

>>> binull (18, 42)
False

>>> binull (Right 42)
False

>>> binull (BiList [] [])
True

Throw an IOError corresponding to the current value of getErrno if the IO action returns nullPtr.

Throw an IOError corresponding to the current value of getErrno if the IO action returns nullPtr, but retry in case of an interrupted operation.

as throwErrnoIfNullRetry, but checks for operations that would block.

as throwErrnoIfNull, but exceptions include the given path when appropriate.

Guards against null pointers