Functional: fn::discard

fn::discard

Fri Apr 18 2025

View On GitHub

Support

Defined in#include <fn/discard.hpp>

Discard the value explicitly.

This is useful when only side-effects are desired and the final value is not needed.

Use through the fn::discard nielbloid.

Call signatures

functor< discard_t >

fn::discard_t

operator()

()

Unconditionally discards the value.

Return value

void

Examples

struct Error final {
  std::string what;
};

...

fn::optional<int> op{42};

op | fn::inspect([](int v) noexcept { REQUIRE(v == 42); })1

   | fn::discard();

1Observe for side-effects only

42 is observed by inspect and the value is discarded by discard (no warning for discarded result of inspect).