MRDOCS_CHECK_OR_CONTINUE

Check a value and skip to the next loop iteration if it failed.

Synopsis

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

#define MRDOCS_CHECK_OR_CONTINUE(var)

Description

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

// Node is the struct from the MRDOCS_CHECK_OR example.
int total = 0;
for (Node const* node : nodes)
{
    MRDOCS_CHECK_OR_CONTINUE(node);         // skip null pointers
    MRDOCS_CHECK_OR_CONTINUE(node->name);   // skip empty names
    MRDOCS_CHECK_OR_CONTINUE(node->n > 0);  // skip non-positive counts
    total += node->n;
}

The loop expands to roughly this (simplified: the real code calls ::mrdocs::detail::failed):

int total = 0;
for (Node const* node : nodes)
{
    // MRDOCS_CHECK_OR_CONTINUE(node);
    if (failed(node)) {         // !node, since node is a pointer
        continue;
    }

    // MRDOCS_CHECK_OR_CONTINUE(node->name);
    if (failed(node->name)) {   // node->name.empty(), a string
        continue;
    }

    // MRDOCS_CHECK_OR_CONTINUE(node->n > 0);
    if (failed(node->n > 0)) {  // the condition is false
        continue;
    }

    total += node->n;
}

The value is evaluated once, so a call expression like MRDOCS_CHECK_OR_CONTINUE(isVisible(node)) is fine.

Things to keep in mind:

Use it only inside a loop, and end it with a semicolon.
The expansion is two statements. Put braces around it when it's the body of an if or else.

Parameters

Name

Description

var

The value to check.

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