Added example for tree traversal

examples/tree_traversal.c

@@ -0,0 +1,73 @@
+#include "../mpc.h"
+
+int main(int argc, char *argv[]) {
+
+    mpc_parser_t *Input  = mpc_new("input");
+    mpc_parser_t *Node  = mpc_new("node");
+    mpc_parser_t *Leaf  = mpc_new("leaf");
+    mpc_ast_t *ast, *tree, *child, *child_sub;
+    mpc_result_t r;
+    int index, lb;
+
+    mpca_lang(MPCA_LANG_PREDICTIVE,
+            " node : '(' <node> ',' /foo/ ',' <node> ')' | <leaf>;"
+            " leaf : /bar/;"
+            " input : /^/ <node> /$/;",
+            Node, Leaf, Input, NULL);
+
+    if (argc > 1) {
+
+        if (mpc_parse_contents(argv[1], Input, &r)) {
+            ast = r.output;
+        } else {
+            mpc_err_print(r.error);
+            mpc_err_delete(r.error);
+            mpc_cleanup(3, Node, Leaf, Input);
+            return EXIT_FAILURE;
+        }
+
+    } else {
+
+        if (mpc_parse_pipe("<stdin>", stdin, Input, &r)) {
+            ast = r.output;
+        } else {
+            mpc_err_print(r.error);
+            mpc_err_delete(r.error);
+            mpc_cleanup(3, Node, Leaf, Input);
+            return EXIT_FAILURE;
+        }
+
+    }
+
+    /* Get index or child of tree */
+    tree = ast->children[1];
+
+    index = mpc_ast_get_index(tree, "node|>");
+    child = mpc_ast_get_child(tree, "node|>");
+
+    if(child == NULL) {
+        mpc_cleanup(3, Node, Leaf, Input);
+        mpc_ast_delete(ast);
+        return EXIT_FAILURE;
+    }
+
+    printf("Index: %d; Child: \"%s\"\n", index, child->tag);
+
+    /* Get multiple indexes or children of trees */
+    index     = mpc_ast_get_index_lb(child, "node|leaf|regex", 0);
+    child_sub = mpc_ast_get_child_lb(child, "node|leaf|regex", 0);
+
+    while(index != -1) {
+        printf("-- Index: %d; Child: \"%s\"\n", index, child_sub->tag);
+
+        lb = index + 1;
+        index     = mpc_ast_get_index_lb(child, "node|leaf|regex", lb);
+        child_sub = mpc_ast_get_child_lb(child, "node|leaf|regex", lb);
+    }
+
+    /* Clean up and return */
+    mpc_cleanup(3, Node, Leaf, Input);
+    mpc_ast_delete(ast);
+
+    return EXIT_SUCCESS;
+}