2.6.5 Pratt構文解析器の実装

src/monkey/parser/parser.go

@@ -7,13 +7,21 @@ import (
 	"monkey/token"
 )
 
+type (
+	prefixParseFn func() ast.Expression
+	infixParseFn  func(ast.Expression) ast.Expression
+)
+
 type Parser struct {
 	l *lexer.Lexer
 
 	curToken  token.Token
 	peekToken token.Token
 
 	errors []string
+
+	prefixParseFns map[token.TokenType]prefixParseFn
+	infixParseFns  map[token.TokenType]infixParseFn
 }
 
 func New(l *lexer.Lexer) *Parser {
@@ -111,3 +119,11 @@ func (p *Parser) peekError(t token.TokenType) {
 	msg := fmt.Sprintf("expected next token to be %s, got %s insted", t, p.peekToken.Type)
 	p.errors = append(p.errors, msg)
 }
+
+func (p *Parser) registerPrefix(tokenType token.TokenType, fn prefixParseFn) {
+	p.prefixParseFns[tokenType] = fn
+}
+
+func (p *Parser) registerInfix(tokenType token.TokenType, fn infixParseFn) {
+	p.infixParseFns[tokenType] = fn
+}

src/monkey/parser/parser_test.go

@@ -8,7 +8,7 @@ import (
 
 func TestLetStatements(t *testing.T) {
 	input := `
-	let x 5;
+	let x = 5;
 	let y = 10;
 	let foobar = 383838;
 	`