Test now passes, wonder what I did wrong.

git-svn-id: https://svn.tlawal.org/svn/monkey@17 f6afcba9-9ef1-4bdd-9b72-7484f5705bac

parser/parser.go

@@ -0,0 +1,86 @@
+package parser
+
+import (
+	"monkey/ast"
+	"monkey/lexer"
+	"monkey/token"
+)
+
+type Parser struct {
+	lexer         *lexer.Lexer
+	current_token token.Token
+	peek_token    token.Token
+}
+
+func New(l_lexer *lexer.Lexer) *Parser {
+	l_parser := &Parser{lexer: l_lexer}
+
+	// Read two tokens so current_token and peek_token are both set
+	l_parser.next_token()
+	l_parser.next_token()
+
+	return l_parser
+}
+
+func (l_parser *Parser) ParseProgram() *ast.Program {
+	program := &ast.Program{}
+	program.Statements = []ast.Statement{}
+
+	for l_parser.current_token.Type != token.EOF {
+		statement := l_parser.parse_statement()
+		if statement != nil {
+			program.Statements = append(program.Statements, statement)
+		}
+		l_parser.next_token()
+	}
+	return program
+}
+
+func (l_parser *Parser) next_token() {
+	l_parser.current_token = l_parser.peek_token
+	l_parser.peek_token = l_parser.lexer.NextToken()
+}
+
+func (l_parser *Parser) parse_statement() ast.Statement {
+	switch l_parser.current_token.Type {
+	case token.LET:
+		return l_parser.parse_let_statement()
+	default:
+		return nil
+	}
+}
+
+func (l_parser *Parser) parse_let_statement() *ast.LetStatement {
+	statement := &ast.LetStatement{Token: l_parser.current_token}
+	if !l_parser.expect_peek(token.IDENT) {
+		return nil
+	}
+
+	statement.Name = &ast.Identifier{Token: l_parser.current_token, Value: l_parser.current_token.Literal}
+	if !l_parser.expect_peek(token.ASSIGN) {
+		return nil
+	}
+
+	// TODO(tijani): Skipping the expressins until there is a semicolon
+	for !l_parser.current_token_is(token.SEMICOLON) {
+		l_parser.next_token()
+	}
+	return statement
+}
+
+func (l_parser *Parser) current_token_is(l_token token.TokenType) bool {
+	return l_parser.current_token.Type == l_token
+}
+
+func (l_parser *Parser) peek_token_is(l_token token.TokenType) bool {
+	return l_parser.peek_token.Type == l_token
+}
+
+func (l_parser *Parser) expect_peek(l_token token.TokenType) bool {
+	if l_parser.peek_token_is(l_token) {
+		l_parser.next_token()
+		return true
+	} else {
+		return false
+	}
+}

parser/parser_test.go

@@ -0,0 +1,67 @@
+package parser
+
+import (
+	"monkey/ast"
+	"monkey/lexer"
+	"testing"
+)
+
+func TestLetStatement(l_test *testing.T) {
+	input := `
+   let x = 4;
+   let y = 19;
+   let foobar = 8948398493;
+  `
+
+	l_lexer := lexer.New(input)
+	l_parser := New(l_lexer)
+
+	program := l_parser.ParseProgram()
+	if program == nil {
+		l_test.Fatalf("ParseProgram() returned nil")
+	}
+
+	if len(program.Statements) != 3 {
+		l_test.Fatalf("program.Statements does not contain 3 statements, got=%d", len(program.Statements))
+	}
+
+	tests := []struct {
+		expected_identifier string
+	}{
+		{"x"},
+		{"y"},
+		{"foobar"},
+	}
+
+	for i, tt := range tests {
+		statement := program.Statements[i]
+		if !testLetStatement(l_test, statement, tt.expected_identifier) {
+			return
+		}
+	}
+}
+
+func testLetStatement(l_test *testing.T, statement ast.Statement, name string) bool {
+	if statement.TokenLiteral() != "let" {
+		l_test.Errorf("statement.TokenLiteral not let, got=%q", statement.TokenLiteral())
+		return false
+	}
+
+	let_statement, ok := statement.(*ast.LetStatement)
+	if !ok {
+		l_test.Errorf("statement not *ast.LetStatement, got=%T", statement)
+		return false
+	}
+
+	if let_statement.Name.Value != name {
+		l_test.Errorf("let_statement.name.Value not %s, got=%s", name, let_statement.Name.Value)
+		return false
+	}
+
+	if let_statement.Name.TokenLiteral() != name {
+		l_test.Errorf("let_statement.name.TokenLiteral() not %s, got=%s", name, let_statement.Name.TokenLiteral())
+		return false
+
+	}
+	return true
+}