Basic structure of the parser, I now understand what is going on. I think ¯\_(?)_/¯

git-svn-id: https://svn.tlawal.org/svn/monkey@14 f6afcba9-9ef1-4bdd-9b72-7484f5705bac

parser/parser.go

@@ -0,0 +1,35 @@
+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, one for curren_token and another for peek_token
+	l_parser.next_token()
+	l_parser.next_token()
+
+	return l_parser
+}
+
+// When this is first called, current_token and peek_token should point to the same
+// token
+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) ParseProgram() *ast.Program {
+	return nil
+}

parser/parser_test.go

@@ -0,0 +1,64 @@
+package parser
+
+import (
+	"monkey/ast"
+	"monkey/lexer"
+	"testing"
+)
+
+func TestLetStatements(t *testing.T) {
+	input := `
+   let x = 5;
+   let y = 10;
+   let foobar = 839893;
+  `
+
+	l_lexer := lexer.New(input)
+	l_parser := New(l_lexer)
+
+	program := l_parser.ParseProgram()
+	if program == nil {
+		t.Fatalf("ParseProgram() returned nil")
+	}
+
+	if len(program.Statements) != 3 {
+		t.Fatalf("program.Statements does not contail 3 statements, got=%d", len(program.Statements))
+	}
+
+	tests := []struct {
+		expectedIdentifier string
+	}{
+		{"x"}, {"y"}, {"foobar"},
+	}
+
+	for i, tt := range tests {
+		stmt := program.Statements[i]
+		if !testLetStatement(t, stmt, tt.expectedIdentifier) {
+			return
+		}
+	}
+}
+
+func testLetStatement(t *testing.T, s ast.Statement, name string) bool {
+	if s.TokenLiteral() != "let" {
+		t.Errorf("s.TokenLiteral not 'let', got=%q", s.TokenLiteral())
+		return false
+	}
+
+	letStmt, ok := s.(*ast.LetStatement)
+	if !ok {
+		t.Errorf("s not *ast.LetStatement, got=%T", s)
+		return false
+	}
+
+	if letStmt.Name.TokenLiteral() != name {
+		t.Errorf("letStmt.Name.TokenLiteral() not '%s', got =%s", name, letStmt.Name.TokenLiteral())
+		return false
+	}
+
+	if letStmt.Name.Value != name {
+		t.Errorf("letStmt.Name.Value not '%s', got =%s", name, letStmt.Name.Value)
+		return false
+	}
+	return true
+}