=proto
int duk_is_boolean(duk_context *ctx, int index);

=stack
[ ... val! ... ]

=summary
<p>Returns 1 if value at <tt>index</tt> is a boolean, otherwise
returns 0.  If <tt>index</tt> is invalid, also returns 0.</p>

=example
if (duk_is_boolean(ctx, -3)) {
    /* ... */
}

=tags
stack