From 82f7e21d3aa02c9a46be311e512ef7a6a1840eb3 Mon Sep 17 00:00:00 2001
From: Brandon Rozek <brozek@mail.umw.edu>
Date: Mon, 24 Sep 2018 14:21:32 -0400
Subject: [PATCH] Added the abilty for lambda expressions to be added into the
 AST. Have not added logic to properly evaulate lambda expressions yet.
 Currently defaults to a long with the value 0.

---
 src/lexer.l  |  2 ++
 src/node.h   |  1 +
 src/parser.y | 20 ++++++++++++++++----
 3 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/src/lexer.l b/src/lexer.l
index 9a75420..f369d48 100644
--- a/src/lexer.l
+++ b/src/lexer.l
@@ -39,6 +39,8 @@ DIGIT [0-9]
 "while"                 {return WHILE;}
 "print"                 {return PRINT;}
 "input"                 {return INPUT;}
+"lambda"                {return LAMBDA;}
+":"                     {return COLON;}
 "true"                  {yylval.value = make_node(VALUE, make_value(BOOLEAN, 1, 0), ""); return VALUE;}
 "false"                 {yylval.value = make_node(VALUE, make_value(BOOLEAN, 0, 0), ""); return VALUE;}
 {DIGIT}                 {yylval.value = make_node(VALUE, make_value(LONG, atoi(yytext), 0), ""); return VALUE;}
diff --git a/src/node.h b/src/node.h
index 2b5546f..f1bdb6e 100644
--- a/src/node.h
+++ b/src/node.h
@@ -4,6 +4,7 @@
 #define ID_SIZE 100
 #define MAX_CHILDREN 3
 #define STATEMENT 200
+#define CALLFUNC 201
 #define MAX_VARIABLES 200
 
 enum TypeTag { DOUBLE, LONG, BOOLEAN };
diff --git a/src/parser.y b/src/parser.y
index 6b84814..2baf386 100644
--- a/src/parser.y
+++ b/src/parser.y
@@ -51,9 +51,11 @@ struct Node* result;
 %token COMMENT            
 %token WHITESPACE   
 %token DONE
+%token <value> LAMBDA
+%token COLON
 
 /* declare non-terminals */
-%type <value> program statement assignment if-statement if-else-statement while print statements substatements expression subexpression term subterm factor atom identvalue ident
+%type <value> program statement assignment if-statement if-else-statement while print statements substatements callfunc expression subexpression term subterm factor atom identvalue ident
 
 /* give us more detailed errors */
 %error-verbose
@@ -135,9 +137,17 @@ atom: OPENPAREM expression ENDPAREM { $$ = $2; }
 
 ident: IDENTIFIER { $$ = $1; }
 
-identvalue: IDENTIFIER { $$ = $1; }
+callfunc: ident OPENPAREM ident ENDPAREM { $$ = make_node(CALLFUNC, NULL, 0); attach_node($$, $1); attach_node($$, $3); }
+
+identvalue: callfunc { $$ = $1; }
+          | ident { $$ = $1; }
           | VALUE { $$ = $1; }
           | INPUT { $$ = make_node(INPUT, NULL , ""); }
+          | LAMBDA ident COLON expression { 
+              // Only supports one argument functions for now
+              $$ = make_node(LAMBDA, NULL, "");
+              attach_node($$, $2);
+              attach_node($$, $4); }
 
 
 
@@ -244,6 +254,7 @@ void print_tree(struct Node* node, int tabs) {
     case WHILE: printf("WHILE:\n"); break;
     case PRINT: printf("PRINT:\n"); break;
     case INPUT: printf("INPUT:\n"); break;
+    case LAMBDA: printf("LAMBDA:\n"); break;
     case STATEMENT: printf("STATEMENT:\n"); break;
     case VALUE: 
       if (node->value->type == BOOLEAN) {
@@ -642,11 +653,11 @@ struct Value* eval_expression(struct Node* node, struct Environment* env) {
   double temp;
   struct Variable* var = NULL;
 
-  // Evaluate subexpressions if existent
+  // Evaluate subexpressions if existent and node is not a lambda expression
   struct Value* val1 = NULL;
   struct Value* val2 = NULL;
   struct Value* val3 = NULL;
-  if (node->num_children > 0) {
+  if (node->num_children > 0 && node->type != LAMBDA) {
     val1 = eval_expression(node->children[0], env);
     if (node->num_children > 1) {
       val2 = eval_expression(node->children[1], env);
@@ -658,6 +669,7 @@ struct Value* eval_expression(struct Node* node, struct Environment* env) {
   }
 
   switch(node->type) {
+    case LAMBDA: printf("<LambdaExpression>\n"); return make_long(0); break;
     case PLUS:
       check_num_nodes(node, 2, "cannot add more than two expressions.");
       return add(val1, val2);