5 files changed, 34 insertions, 15 deletions
diff --git a/bu-parser.c b/bu-parser.c
index b077938..df4c2c2 100644
--- a/bu-parser.c
+++ b/bu-parser.c
@@ -2,12 +2,6 @@
 #include "tree.h"
 #include <stdio.h>
 
-void free_node(node *n) {
-  if (n->lhs) free_node(n->lhs);
-  if (n->rhs) free_node(n->rhs);
-  free(n);
-}
-
 void fprint_stack(FILE *stream, struct expr_parser *ep) {
   for (size_t i = 0; i < ep->stack_idx; i++) {
     struct stackmember m = ep->stack[i];
@@ -132,6 +126,20 @@ void unary_expr(struct expr_parser *ep) {
   ep->stack[ep->stack_idx - 1] = newm;
 }
 
+void parens_expr(struct expr_parser *ep) {
+  struct stackmember o, e, c;
+  o = stack_pos(ep, 2);
+  e = stack_pos(ep, 1);
+  c = stack_pos(ep, 0);
+  BAIL_REDUCE_IF(
+    o.id != TOKEN_OPEN_PAREN
+    || e.id != STACKMEMBER_EXPR
+    || c.id != TOKEN_CLOSE_PAREN, "mismatched parenthesis");
+
+  ep->stack_idx -= 2;
+  ep->stack[ep->stack_idx - 1] = e;
+}
+
 int expr_parser_run(struct expr_parser *ep) {
   // prime the look-ahead
   ep->lahead = ep->lex(ep->lex_data);
@@ -167,6 +175,10 @@ int expr_parser_run(struct expr_parser *ep) {
           }
         }
         break;
+      case TOKEN_CLOSE_PAREN:
+        parens_expr(ep);
+        noshift = 1;
+        break;
       default: break;
     }
   }
diff --git a/bu-parser.h b/bu-parser.h
index 7dc7034..8910b5d 100644
--- a/bu-parser.h
+++ b/bu-parser.h
@@ -7,17 +7,10 @@
 #include "tree.h"
 
 /* PRODUCTION RULES
-
-  <expr> ::= <expr> <binary_op> <expr> | <unary_op> <expr> | <var>
+  <expr> ::= <expr> <binary_op> <expr> | <unary_op> <expr> | "(" <expr> ")" | <var>
   <binary_op> ::= "*" | "+"
   <unary_op> ::= "!"
   <var> ::= r#[a-z]
-
- */
-
-/* POSSIBILITIES
-  a-z => var
-  
  */
 
 enum parser_state {
@@ -31,6 +24,8 @@ enum token_id {
   TOKEN_BINARY_OPERATOR,
   TOKEN_UNARY_OPERATOR,
   TOKEN_VARIABLE,
+  TOKEN_OPEN_PAREN,
+  TOKEN_CLOSE_PAREN,
   TOKEN_EOS,
   TOKEN_OOB,
   TOKEN_MAX,
diff --git a/main.c b/main.c
index 5d51875..0477bae 100644
--- a/main.c
+++ b/main.c
@@ -23,6 +23,8 @@ struct chartoken lex_str(void *v) {
       case '!': token.id = TOKEN_UNARY_OPERATOR; break;
       case '*':
       case '+': token.id = TOKEN_BINARY_OPERATOR; break;
+      case '(': token.id = TOKEN_OPEN_PAREN; break;
+      case ')': token.id = TOKEN_CLOSE_PAREN; break;
       default: break;
     }
   }
@@ -36,7 +38,9 @@ int main(){
   scanf("%[^\n]", str);
   char str2[100];
   strncpy(str2, str, 100);
-  printTree(parse(str2),0);
+  node *exp = parse(str2);
+  printTree(exp,0);
+  free_node(exp);
 
   struct lex_str_data lxd;
   lxd.str = str;
diff --git a/tree.c b/tree.c
index b53ece2..fbb561a 100644
--- a/tree.c
+++ b/tree.c
@@ -62,3 +62,10 @@ void fprintTree(FILE *stream, node *root, int level) {
 void printTree(node *root, int level) {
   fprintTree(stdout, root, level);
 }
+
+void free_node(node *n) {
+  if (n->lhs) free_node(n->lhs);
+  if (n->rhs) free_node(n->rhs);
+  free(n);
+}
+
diff --git a/tree.h b/tree.h
index 8df9f53..c18ccae 100644
--- a/tree.h
+++ b/tree.h
@@ -23,5 +23,6 @@ typedef struct node {
 node * parse(char *str);
 void fprintTree(FILE *stream, node *root, int level);
 void printTree(node *root, int level);
+void free_node(node *n);
 
 #endif