From 612c680e2ab7e15723a7443e6378e264f7aafc60 Mon Sep 17 00:00:00 2001
From: "Michael D. Lowis" <mike.lowis@gentex.com>
Date: Mon, 25 Jun 2018 14:33:13 -0400
Subject: [PATCH] first attempt at if statement parsing

---
 example.src     |  5 +++++
 source/lexer.l  |  2 ++
 source/parser.c | 31 +++++++++++++++++++++++++++----
 source/sclpl.h  |  2 +-
 4 files changed, 35 insertions(+), 5 deletions(-)

diff --git a/example.src b/example.src
index c6f51e6..f1885fd 100644
--- a/example.src
+++ b/example.src
@@ -36,6 +36,11 @@ fun main(args string[]) int {
     foo();
     bar(1);
     baz(1,2);
+#    if (123) {}
+#    if 123 {}
+#    if (123) {} else {}
+#    if (123) {} else if {}
+#    if (123) {} else if {} else {}
     return bar;
 }
 
diff --git a/source/lexer.l b/source/lexer.l
index 22dc4e9..ce19730 100644
--- a/source/lexer.l
+++ b/source/lexer.l
@@ -44,6 +44,8 @@ NOSPACE [^ \t\r\n]
 "struct"  { return T_STRUCT;   }
 "union"   { return T_UNION;    }
 "return"  { return T_RETURN;   }
+"if"      { return T_IF;       }
+"else"    { return T_ELSE;     }
 
 "("    { return '(';    }
 ")"    { return ')';    }
diff --git a/source/parser.c b/source/parser.c
index ac282d2..16fc84a 100644
--- a/source/parser.c
+++ b/source/parser.c
@@ -13,6 +13,8 @@ static AST* expression_block(Parser* p);
 static AST* statement(Parser* p);
 static AST* expression(Parser* p);
 static AST* definition(Parser* p, bool constant);
+static AST* return_statement(Parser* p);
+static AST* if_statement(Parser* p);
 static AST* func_expr_list(Parser* p);
 
 static AST* const_expression(Parser* p);
@@ -221,10 +223,10 @@ static AST* statement(Parser* p) {
     } else {
         if (matches(p, T_LET) || matches(p, T_VAR)) {
             definition(p, (peek(p)->type == T_LET));
-        } else if (accept(p, T_RETURN)) {
-            expression(p);
-            expect(p, ';');
-//        } else if (matches(p, T_IF)) {
+        } else if (matches(p, T_RETURN)) {
+            return_statement(p);
+        } else if (matches(p, T_IF)) {
+            if_statement(p);
 //        } else if (matches(p, T_WHILE)) {
 //        } else if (matches(p, T_FOR)) {
 //        } else if (matches(p, T_DO)) {
@@ -264,6 +266,27 @@ static AST* definition(Parser* p, bool constant) {
     return NULL;
 }
 
+static AST* return_statement(Parser* p) {
+    expect(p, T_RETURN);
+    expression(p);
+    expect(p, ';');
+    return NULL;
+}
+
+static AST* if_statement(Parser* p) {
+    expect(p, T_IF);
+    expression(p);
+    expression_block(p);
+    if (accept(p, T_ELSE)) {
+        if (matches(p, T_IF)) {
+            if_statement(p);
+        } else {
+            expression_block(p);
+        }
+    }
+    return NULL;
+}
+
 static AST* func_expr_list(Parser* p) {
     expect(p, '(');
     if (!matches(p, ')')) {
diff --git a/source/sclpl.h b/source/sclpl.h
index aa3cea8..069e116 100644
--- a/source/sclpl.h
+++ b/source/sclpl.h
@@ -42,7 +42,7 @@ void vec_set(vec_t* vec, size_t index, void* data);
 typedef enum {
     T_NONE = 0, T_ERROR = 256, T_END_FILE,
     T_PACKAGE, T_REQUIRES, T_PROVIDES, T_LET, T_VAR, T_FUN, T_TYPE, T_STRUCT,
-    T_UNION, T_RETURN,
+    T_UNION, T_RETURN, T_IF, T_ELSE,
     T_ID, T_CHAR, T_INT, T_FLOAT, T_BOOL, T_STRING,
 } TokType;
 
-- 
2.52.0