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
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35
parser/parser.go
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35
parser/parser.go
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package parser
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import (
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"monkey/ast"
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"monkey/lexer"
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"monkey/token"
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)
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type Parser struct {
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lexer *lexer.Lexer
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current_token token.Token
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peek_token token.Token
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}
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func New(l_lexer *lexer.Lexer) *Parser {
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l_parser := &Parser{lexer: l_lexer}
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// Read two tokens, one for curren_token and another for peek_token
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l_parser.next_token()
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l_parser.next_token()
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return l_parser
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}
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// When this is first called, current_token and peek_token should point to the same
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// token
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func (l_parser *Parser) next_token() {
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l_parser.current_token = l_parser.peek_token
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l_parser.peek_token = l_parser.lexer.NextToken()
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}
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func (l_parser *Parser) ParseProgram() *ast.Program {
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return nil
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}
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64
parser/parser_test.go
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64
parser/parser_test.go
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package parser
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import (
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"monkey/ast"
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"monkey/lexer"
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"testing"
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)
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func TestLetStatements(t *testing.T) {
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input := `
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let x = 5;
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let y = 10;
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let foobar = 839893;
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`
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l_lexer := lexer.New(input)
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l_parser := New(l_lexer)
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program := l_parser.ParseProgram()
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if program == nil {
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t.Fatalf("ParseProgram() returned nil")
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}
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if len(program.Statements) != 3 {
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t.Fatalf("program.Statements does not contail 3 statements, got=%d", len(program.Statements))
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}
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tests := []struct {
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expectedIdentifier string
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}{
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{"x"}, {"y"}, {"foobar"},
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}
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for i, tt := range tests {
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stmt := program.Statements[i]
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if !testLetStatement(t, stmt, tt.expectedIdentifier) {
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return
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}
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}
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}
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func testLetStatement(t *testing.T, s ast.Statement, name string) bool {
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if s.TokenLiteral() != "let" {
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t.Errorf("s.TokenLiteral not 'let', got=%q", s.TokenLiteral())
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return false
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}
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letStmt, ok := s.(*ast.LetStatement)
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if !ok {
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t.Errorf("s not *ast.LetStatement, got=%T", s)
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return false
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}
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if letStmt.Name.TokenLiteral() != name {
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t.Errorf("letStmt.Name.TokenLiteral() not '%s', got =%s", name, letStmt.Name.TokenLiteral())
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return false
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}
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if letStmt.Name.Value != name {
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t.Errorf("letStmt.Name.Value not '%s', got =%s", name, letStmt.Name.Value)
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return false
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}
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return true
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}
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