new AST built with sum types

vlib/compiler2/parser/parser.v

@@ -0,0 +1,81 @@
+// Copyright (c) 2019 Alexander Medvednikov. All rights reserved.
+// Use of this source code is governed by an MIT license
+// that can be found in the LICENSE file.
+module parser
+
+import (
+	compiler2.scanner
+	compiler2.ast
+	compiler2.token
+)
+
+struct Parser {
+	scanner &scanner.Scanner
+mut:
+	tok token.Token
+	lit string
+}
+
+pub fn parse_expr(text string) ast.Expr {
+	mut s := scanner.new_scanner(text)
+	res := s.scan()
+	mut p := Parser{
+		scanner: s
+		tok: res.tok
+		lit: res.lit
+	}
+	return p.expr()
+}
+
+fn (p mut Parser) next() {
+	res := p.scanner.scan()
+	p.tok = res.tok
+	//println(p.tok.str())
+	p.lit = res.lit
+}
+
+fn (p mut Parser) expr() ast.Expr {
+	//println('\n\nexpr()')
+	mut node := p.term()
+	for p.tok == .plus || p.tok == .minus {
+		op := p.tok
+		p.next()
+		node = ast.BinaryExpr {
+			left: node
+			op: op
+			right: p.term()
+		}
+	}
+	return node
+}
+
+fn (p mut Parser) term() ast.Expr {
+	mut node := p.factor()
+	for p.tok == .mul || p.tok == .div || p.tok == .mod {
+		op := p.tok
+		p.next()
+		node = ast.BinaryExpr {
+			left: node
+			op: op
+			right: p.factor()
+		}
+	}
+	return node
+	//return ast.BinaryExpr{}
+	//return ast.Expr.Binary(ast.BinaryExpr{})
+}
+
+fn (p mut Parser) factor() ast.Expr {
+	if p.tok == .number {
+		val := p.lit.int()
+		p.next()
+		return ast.IntegerExpr { val: val }
+	} else {
+		println('bad factor token')
+		println(p.tok)
+		exit(1)
+	}
+}
+
+
+

vlib/compiler2/parser/parser_test.v

@@ -0,0 +1,35 @@
+module parser
+
+import compiler2.ast
+
+fn test_parser() {
+	//expr := ast.IntegerExpr {val:10}
+	//expr := ast.BinaryExpr{}
+	expr := parse_expr('3 + 7')
+	walk(expr)
+	println('')
+}
+
+fn walk(node ast.Expr) {
+	//println('walk()')
+	match node {
+		ast.IntegerExpr {
+			print(it.val)
+		}
+		ast.BinaryExpr {
+			walk(it.left)
+			match it.op {
+				.plus {
+					print(' + ')
+				}
+				.minus {
+					print(' - ')
+				}
+				else {}
+
+			}
+			walk(it.right)
+		}
+		else {}
+	}
+}