Parsing prefix expressions, tests passes
git-svn-id: https://svn.tlawal.org/svn/monkey@24 f6afcba9-9ef1-4bdd-9b72-7484f5705bac
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45f6929c14
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22
ast/ast.go
22
ast/ast.go
@ -58,6 +58,12 @@ type IntegerLiteral struct {
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Value int64
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Value int64
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}
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}
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type PrefixExpression struct {
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Token token.Token // prefix token i.e. !
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Operator string
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Right Expression
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}
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// Let Statements
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// Let Statements
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func (ls *LetStatement) statement_node() {}
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func (ls *LetStatement) statement_node() {}
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@ -139,3 +145,19 @@ func (il *IntegerLiteral) TokenLiteral() string {
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func (il *IntegerLiteral) String() string {
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func (il *IntegerLiteral) String() string {
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return il.Token.Literal
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return il.Token.Literal
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}
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}
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// PrefixExpression
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func (pe *PrefixExpression) expression_node() {}
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func (pe *PrefixExpression) TokenLiteral() string {
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return pe.Token.Literal
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}
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func (pe *PrefixExpression) String() string {
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var out bytes.Buffer
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out.WriteString("(")
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out.WriteString(pe.Operator)
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out.WriteString(pe.Right.String())
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out.WriteString(")")
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return out.String()
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}
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@ -47,6 +47,8 @@ func New(l_lexer *lexer.Lexer) *Parser {
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l_parser.prefix_parse_functions = make(map[token.TokenType]prefix_parse_function)
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l_parser.prefix_parse_functions = make(map[token.TokenType]prefix_parse_function)
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l_parser.register_prefix(token.IDENT, l_parser.parse_identifier)
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l_parser.register_prefix(token.IDENT, l_parser.parse_identifier)
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l_parser.register_prefix(token.INT, l_parser.parse_integer_literal)
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l_parser.register_prefix(token.INT, l_parser.parse_integer_literal)
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l_parser.register_prefix(token.BANG, l_parser.parse_prefix_expression)
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l_parser.register_prefix(token.MINUS, l_parser.parse_prefix_expression)
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return l_parser
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return l_parser
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}
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}
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@ -69,16 +71,17 @@ func (l_parser *Parser) ParseProgram() *ast.Program {
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return program
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return program
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}
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}
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func (l_parser *Parser) register_prefix(l_token_type token.TokenType, l_function prefix_parse_function) {
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func (l_parser *Parser) peek_error(l_token token.TokenType) {
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l_parser.prefix_parse_functions[l_token_type] = l_function
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message := fmt.Sprintf("expected next token to be %s, got %s", l_token, l_parser.peek_token.Type)
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l_parser.errors = append(l_parser.errors, message)
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}
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}
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func (l_parser *Parser) parse_identifier() ast.Expression {
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func (l_parser *Parser) current_token_is(l_token token.TokenType) bool {
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return &ast.Identifier{Token: l_parser.current_token, Value: l_parser.current_token.Literal}
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return l_parser.current_token.Type == l_token
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}
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}
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func (l_parser *Parser) register_infix(l_token_type token.TokenType, l_function infix_parse_function) {
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func (l_parser *Parser) peek_token_is(l_token token.TokenType) bool {
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l_parser.infix_parse_functions[l_token_type] = l_function
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return l_parser.peek_token.Type == l_token
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}
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}
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func (l_parser *Parser) next_token() {
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func (l_parser *Parser) next_token() {
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@ -86,6 +89,16 @@ func (l_parser *Parser) next_token() {
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l_parser.peek_token = l_parser.lexer.NextToken()
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l_parser.peek_token = l_parser.lexer.NextToken()
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}
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}
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func (l_parser *Parser) expect_peek(l_token token.TokenType) bool {
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if l_parser.peek_token_is(l_token) {
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l_parser.next_token()
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return true
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} else {
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l_parser.peek_error(l_token)
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return false
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}
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}
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func (l_parser *Parser) parse_statement() ast.Statement {
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func (l_parser *Parser) parse_statement() ast.Statement {
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switch l_parser.current_token.Type {
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switch l_parser.current_token.Type {
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case token.LET:
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case token.LET:
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@ -135,6 +148,18 @@ func (l_parser *Parser) parse_expression_statement() *ast.ExpressionStatement {
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return statement
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return statement
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}
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}
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func (l_parser *Parser) register_prefix(l_token_type token.TokenType, l_function prefix_parse_function) {
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l_parser.prefix_parse_functions[l_token_type] = l_function
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}
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func (l_parser *Parser) parse_identifier() ast.Expression {
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return &ast.Identifier{Token: l_parser.current_token, Value: l_parser.current_token.Literal}
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}
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func (l_parser *Parser) register_infix(l_token_type token.TokenType, l_function infix_parse_function) {
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l_parser.infix_parse_functions[l_token_type] = l_function
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}
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func (l_parser *Parser) parse_integer_literal() ast.Expression {
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func (l_parser *Parser) parse_integer_literal() ast.Expression {
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literal := &ast.IntegerLiteral{Token: l_parser.current_token}
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literal := &ast.IntegerLiteral{Token: l_parser.current_token}
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value, error := strconv.ParseInt(l_parser.current_token.Literal, 0, 64)
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value, error := strconv.ParseInt(l_parser.current_token.Literal, 0, 64)
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@ -150,31 +175,24 @@ func (l_parser *Parser) parse_integer_literal() ast.Expression {
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func (l_parser *Parser) parse_expression(precedence int) ast.Expression {
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func (l_parser *Parser) parse_expression(precedence int) ast.Expression {
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prefix := l_parser.prefix_parse_functions[l_parser.current_token.Type]
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prefix := l_parser.prefix_parse_functions[l_parser.current_token.Type]
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if prefix == nil {
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if prefix == nil {
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l_parser.no_prefix_parse_function_error(l_parser.current_token.Type)
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return nil
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return nil
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}
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}
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left_expression := prefix()
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left_expression := prefix()
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return left_expression
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return left_expression
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}
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}
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func (l_parser *Parser) expect_peek(l_token token.TokenType) bool {
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func (l_parser *Parser) no_prefix_parse_function_error(l_token_type token.TokenType) {
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if l_parser.peek_token_is(l_token) {
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message := fmt.Sprintf("no prefix parse function for %s, found", l_token_type)
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l_parser.next_token()
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return true
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} else {
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l_parser.peek_error(l_token)
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return false
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}
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}
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func (l_parser *Parser) peek_error(l_token token.TokenType) {
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message := fmt.Sprintf("expected next token to be %s, got %s", l_token, l_parser.peek_token.Type)
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l_parser.errors = append(l_parser.errors, message)
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l_parser.errors = append(l_parser.errors, message)
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}
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}
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func (l_parser *Parser) current_token_is(l_token token.TokenType) bool {
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func (l_parser *Parser) parse_prefix_expression() ast.Expression {
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return l_parser.current_token.Type == l_token
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expression := &ast.PrefixExpression{
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}
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Token: l_parser.current_token,
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Operator: l_parser.current_token.Literal,
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func (l_parser *Parser) peek_token_is(l_token token.TokenType) bool {
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}
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return l_parser.peek_token.Type == l_token
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l_parser.next_token()
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expression.Right = l_parser.parse_expression(PREFIX)
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return expression
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}
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}
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@ -1,6 +1,8 @@
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package parser
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package parser
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import (
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import (
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"fmt"
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"monkey/ast"
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"monkey/ast"
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"monkey/lexer"
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"monkey/lexer"
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"testing"
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"testing"
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@ -175,3 +177,61 @@ func TestIntegerLiteralExpressions(l_test *testing.T) {
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l_test.Errorf("literal.TokenLiteral not %s, got=%s", "5", literal.TokenLiteral())
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l_test.Errorf("literal.TokenLiteral not %s, got=%s", "5", literal.TokenLiteral())
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}
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}
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}
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}
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func TestParsingPrefixExpression(l_test *testing.T) {
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prefix_tests := []struct {
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input string
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operator string
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integer_value int64
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}{
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{"!5;", "!", 5},
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{"-15", "-", 15},
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}
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for _, tt := range prefix_tests {
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l_lexer := lexer.New(tt.input)
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l_parser := New(l_lexer)
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program := l_parser.ParseProgram()
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check_parser_errors(l_test, l_parser)
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if len(program.Statements) != 1 {
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l_test.Fatalf("program.Statements does not contain %d statements, got=%d\n", 1, len(program.Statements))
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}
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statement, ok := program.Statements[0].(*ast.ExpressionStatement)
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if !ok {
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l_test.Fatalf("program.Statements[0] is not ast.ExpressionStatement, got=%T", program.Statements[0])
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}
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expression, ok := statement.Expression.(*ast.PrefixExpression)
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if !ok {
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l_test.Fatalf("program.Statements[0] is not ast.PrefixEXpression, got=%T", statement.Expression)
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}
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if expression.Operator != tt.operator {
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l_test.Fatalf("exp.Operator is not '%s', got %s", tt.operator, expression.Operator)
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}
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if !testIntegerLiteral(l_test, expression.Right, tt.integer_value) {
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return
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}
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}
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}
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func testIntegerLiteral(l_test *testing.T, il ast.Expression, value int64) bool {
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integer, ok := il.(*ast.IntegerLiteral)
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if !ok {
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l_test.Errorf("il not *ast.IntegerLiteral, got=%T", il)
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return false
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}
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if integer.Value != value {
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l_test.Errorf("integer.Value not %d, got=%d", value, integer.Value)
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return false
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}
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if integer.TokenLiteral() != fmt.Sprintf("%d", value) {
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l_test.Errorf("integer.TokenLiteral not %d, got=%s", value, integer.TokenLiteral())
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return false
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}
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return true
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}
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