+++
title = "`bool operator==(const failure_type<A, B> &) const`"
description = "Returns true if this outcome compares equal to the failure type sugar. Constexpr and noexcept propagating."
categories = ["comparisons"]
weight = 820
+++

Returns true if this outcome is unsuccessful and its error compares equal to the error in the failure type sugar. Comparison is done using `operator==` on `error_type` and `A` and on `exception_type` and `B`.

*Requires*: `operator==` must be a valid expression between `error_type` and `A`, or `A` is `void`; `operator==` must be a valid expression between `exception_type` and `B`, or `B` is `void`. If `error_type` is `void`, then so must be `A`; if `exception_type` is `void`, then so must be `B`.

*Complexity*: Whatever the underlying `operator==` has. Constexpr and noexcept of underlying operations is propagated.

*Guarantees*: None.