Make the has string and has vector functions public.

src/tree.c

@@ -1,22 +1,22 @@
 #include "tree.h"
 #include <stdlib.h>
 
-int _tree_has_vector(libab_tree* tree) {
-    return tree->variant == BASE || tree->variant == OP ||
-            tree->variant == UNARY_OP || tree->variant == BLOCK ||
-            tree->variant == IF;
+int libab_tree_has_vector(libab_tree_variant variant) {
+    return variant == BASE || variant == OP ||
+            variant == UNARY_OP || variant == BLOCK ||
+            variant == IF;
+}
+
+int libab_tree_has_string(libab_tree_variant variant) {
+    return variant == ID || variant == NUM ||
+            variant == OP || variant == UNARY_OP;
 }
 
 void libab_tree_free(libab_tree* tree) {
     int free_string = 0;
     int free_vector = 0;
-    if(_tree_has_vector(tree)) {
-        free_vector = 1;
-    }
-    if(tree->variant == ID || tree->variant == NUM ||
-            tree->variant == OP || tree->variant == UNARY_OP) {
-        free_string = 1;
-    }
+    free_vector = libab_tree_has_vector(tree->variant);
+    free_string = libab_tree_has_string(tree->variant);
     if(free_string) free(tree->string_value);
     if(free_vector) vec_free(&tree->children);
 }
@@ -27,7 +27,7 @@ int _tree_foreach_free(void* data, va_list args) {
 }
 
 void libab_tree_free_recursive(libab_tree* tree) {
-    if(_tree_has_vector(tree)) {
+    if(libab_tree_has_vector(tree->variant)) {
         vec_foreach(&tree->children, NULL, compare_always, _tree_foreach_free);
     }
     libab_tree_free(tree);