Slightly improved version of the parser

cclox_src/main.cc

@@ -17,13 +17,22 @@ int main(int argc, char *argv[]) {
   //
   // run_interpreter(argc, argv);
 
-  ExprPtr literal = std::make_shared<Expr>(ExprType::LITERAL, Literal{123});
-  ExprPtr left = std::make_shared<Expr>(ExprType::UNARY, Unary{Token{TokenType::MINUS, "-", Object{}, 1}, literal});
+  ExprPtr left = std::make_shared<Expr>(
+    make_expr(
+      Unary{
+        Token{TokenType::MINUS, "-", Object{}, 1},
+        std::make_shared<Expr>(make_expr(Literal{123}))
+      }
+    )
+  );
 
   Token op{TokenType::STAR, "*", Object{}, 1};
 
-  ExprPtr gliteral = std::make_shared<Expr>(ExprType::LITERAL, Literal{45.67});
-  ExprPtr right = std::make_shared<Expr>(ExprType::GROUPING, gliteral);
+  ExprPtr right = std::make_shared<Expr>(
+    make_expr(
+      Grouping{std::make_shared<Expr>(make_expr(Literal{45.67}))}
+    )
+  );
 
   Expr expr = {ExprType::BINARY, Binary{left, op, right}};
 

cclox_src/parser/expr.cc

@@ -5,6 +5,26 @@
 #include <vector>
 #include <sstream>
 
+template <>
+Expr make_expr<Binary>(Binary value) {
+  return Expr(ExprType::BINARY, value);
+}
+
+template <>
+Expr make_expr<Grouping>(Grouping value) {
+  return Expr(ExprType::GROUPING, value);
+}
+
+template <>
+Expr make_expr<Literal>(Literal value) {
+  return Expr(ExprType::LITERAL, value);
+}
+
+template <>
+Expr make_expr<Unary>(Unary value) {
+  return Expr(ExprType::UNARY, value);
+}
+
 std::string AstPrinter::print(const Expr &expr) {
   switch (expr.type) {
     case ExprType::BINARY: {

cclox_src/parser/expr.hh

@@ -52,6 +52,9 @@ struct Expr {
   Expression value;
 };
 
+template <typename T>
+Expr make_expr(T value);
+
 class AstPrinter {
 public:
   std::string print(const Expr &expr);