compiler2: proof of concept cgen

vlib/compiler2/cgen/cgen.v

@@ -0,0 +1,82 @@
+module cgen
+
+import (
+	strings
+	compiler2.ast
+)
+
+struct Gen {
+	out strings.Builder
+
+}
+
+pub fn gen(program ast.Program) {
+	mut g := Gen{out:strings.new_builder(100)}
+	for expr in program.exprs {
+		g.expr(expr)
+		g.writeln('')
+	}
+	println(g.out.str())
+}
+
+pub fn (g &Gen) save() {
+
+}
+
+pub fn (g mut Gen) write(s string) {
+	g.out.write(s)
+}
+
+pub fn (g mut Gen) writeln(s string) {
+	g.out.writeln(s)
+}
+
+struct Type {
+	name string
+}
+
+const (
+	string_type = Type{'string'}
+	int_type = Type{'int'}
+	void_type = Type{'void'}
+)
+
+fn (g mut Gen) expr(node ast.Expr) Type {
+	//println('cgen expr()')
+	match node {
+		ast.IntegerExpr {
+			g.write(it.val.str())
+			return int_type
+		}
+		ast.StringLiteral {
+			g.write('"$it.val"')
+			return string_type
+		}
+		ast.BinaryExpr {
+			typ := g.expr(it.left)
+			match it.op {
+				.plus {	g.write(' + ')	}
+				.minus {	g.write(' - ')	}
+				.mul {	g.write(' * ')	}
+				.div {	g.write(' / ')	}
+				else {}
+			}
+			typ2 := g.expr(it.right)
+			if typ.name != typ2.name {
+				println('bad types $typ.name $typ2.name')
+			}
+			return typ
+		}
+		ast.VarDecl {
+			g.write('var $it.name = ')
+			g.expr(it.expr)
+			g.writeln(';')
+			return void_type
+		}
+		else {
+			println('bad node')
+		}
+	}
+	return void_type
+}
+