-/* Returns the index of the variable in VS named NAME, or -1 if
- VS contains no variable with that name. */
-static int
-array_var_set_lookup_var_idx (const struct var_set *vs, const char *name)
+/* If VS contains a variable named NAME, sets *IDX to its index
+ and returns true. Otherwise, returns false. */
+static bool
+array_var_set_lookup_var_idx (const struct var_set *vs, const char *name,
+ size_t *idx)