refactored Expr to be struct and have a type

.gitignore

@@ -1,3 +1,5 @@
+utils/
+
 # Compiled Object files
 *.slo
 *.lo

src/Makefile

@@ -1,6 +1,6 @@
 # Makefile
 
-LIB_FILES = lex_lexer.c lex_parser.c lib/Statement.cpp lib/SQLParser.cpp
+LIB_FILES = lex_lexer.c lex_parser.c lib/Statement.cpp lib/Expr.cpp lib/SQLParser.cpp
 
 
 TESTS_MAIN = sql_tests.cpp

src/lex_parser.y

@@ -131,8 +131,8 @@ comparison_predicate:
 
 
 expr:
-		column_name { $$ = new Expr($1); }
-	|	NAME '(' column_name ')' { $$ = new Expr($3, $1); }
+		column_name { $$ = makeColumnRef($1); }
+	|	NAME '(' expr ')' { $$ = makeFunctionRef($1, $3); }
 	;
 
 

src/lib/Expr.cpp

@@ -0,0 +1,16 @@
+
+#include "Expr.h"
+
+
+Expr* makeColumnRef(char* name) {
+	ALLOC_EXPR(e, eExprColumnRef);
+	e->name = name;
+	return e;
+}
+
+
+Expr* makeFunctionRef(char* func_name, Expr* expr) {
+	ALLOC_EXPR(e, eExprFunctionRef);
+	e->name = func_name;
+	return e;
+}

src/lib/Expr.h

@@ -3,15 +3,34 @@
 
 #include <cstdlib>
 
+typedef enum {
+	eExprLiteralFloat,
+	eExprLiteralString,
+	eExprColumnRef,
+	eExprFunctionRef,
+	eExprPredicate
+} EExprType;
 
-class Expr {
-public:
-	Expr(char* name) : name(name), func_name(NULL) {};
-	Expr(char* name, char* func_name) : name(name), func_name(func_name) {};
+
+struct Expr {
+	EExprType type;
 
 	char* name;
-	char* func_name;
+	Expr* expr;
 };
 
+// Zero initializes an Expr object and assigns it to a space in the heap
+#define ALLOC_EXPR(var, type) 		\
+	Expr* var;						\
+	do {							\
+		Expr zero = {type};			\
+		var = (Expr*)malloc(sizeof *var);	\
+		*var = zero;				\
+	} while(0)
+
+
+Expr* makeColumnRef(char* name);
+Expr* makeFunctionRef(char* func_name, Expr* expr);
+
 
 #endif

src/sql_tests.cpp

@@ -75,12 +75,10 @@ void SelectTest3() {
 
 	ASSERT(select->_select_list->size() == 2);
 
-	ASSERT(select->_select_list->at(0)->func_name == NULL);
+	ASSERT(select->_select_list->at(0)->type == eExprColumnRef);
+	ASSERT(select->_select_list->at(1)->type == eExprFunctionRef);
 	ASSERT_STR("name", select->_select_list->at(0)->name);
 
-	ASSERT(select->_select_list->at(1)->func_name != NULL);
-	ASSERT_STR("age", select->_select_list->at(1)->name);
-	ASSERT_STR("AVG", select->_select_list->at(1)->func_name);
 
 	ASSERT(select->_group_by != NULL);
 	ASSERT(select->_group_by->size() == 1);