[#MRDOCS_CHECK_OR_BREAK]
= MRDOCS_CHECK_OR_BREAK
:mrdocs:

Check a value and leave the enclosing loop if it failed.

== Synopsis

Declared in `<mrdocs/Support/Error/Expected.hpp>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
#define MRDOCS_CHECK_OR_BREAK(var)

----

== Description

If the value failed, the macro runs `break`. See `MRDOCS_TRY` for what counts as failed.

[,cpp]
----
// Count the leading results that succeeded.
std::size_t n = 0;
for (Expected<int> const& r : results)
{
    MRDOCS_CHECK_OR_BREAK(r);   // stop at the first error
    ++n;
}
----
The loop expands to roughly this (simplified&colon; the real code calls `&colon;&colon;mrdocs&colon;&colon;detail&colon;&colon;failed`)&colon;

[,cpp]
----
std::size_t n = 0;
for (Expected<int> const& r : results)
{
    // MRDOCS_CHECK_OR_BREAK(r);
    if (failed(r)) {   // !r, since r is an Expected
        break;
    }

    ++n;
}
----
The value is evaluated once, so a call expression is fine&period;

Things to keep in mind&colon;

* Use it only inside a loop or `switch`, and end it with a semicolon&period;
* It&apos;s a plain `break`, so inside a `switch` it leaves the `switch`, not the loop around it&period;
* The expansion is two statements&period; Put braces around it when it&apos;s the body of an `if` or `else`&period;

== Parameters

[cols="1,4"]
|===
| Name| Description
| *var*
| The value to check&period;
|===


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