=proto
duk_bool_t duk_is_nan(duk_context *ctx, duk_idx_t index);

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

=summary
<p>Returns 1 if value at <code>index</code> is a <code>NaN</code> (a special
number value), otherwise returns 0.  If <code>index</code> is invalid,
also returns 0.</p>

<p>IEEE has a large number of different <code>NaN</code> values.  Duktape
normalizes <code>NaN</code> values internally.  This function returns 1
for any kind of a <code>NaN</code>.</p>

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

=tags
stack

=introduced
1.0.0