2.8: Add call expressions

ast/ast.go

@@ -227,3 +227,27 @@ func (fl *FunctionLiteral) String() string {
 
 	return out.String()
 }
+
+type CallExpression struct {
+	Token     token.Token // then '(' token
+	Function  Expression  // Identifier or FunctionLiteral
+	Arguments []Expression
+}
+
+func (ce *CallExpression) expressionNode()      {}
+func (ce *CallExpression) TokenLiteral() string { return ce.Token.Literal }
+func (ce *CallExpression) String() string {
+	var out bytes.Buffer
+
+	var args []string
+	for _, a := range ce.Arguments {
+		args = append(args, a.String())
+	}
+
+	out.WriteString(ce.Function.String())
+	out.WriteString("(")
+	out.WriteString(strings.Join(args, ", "))
+	out.WriteString(")")
+
+	return out.String()
+}

parser/parser.go

@@ -28,6 +28,7 @@ var precedences = map[token.TokenType]int{
 	token.MINUS:    SUM,
 	token.SLASH:    PRODUCT,
 	token.ASTERISK: PRODUCT,
+	token.LPAREN:   CALL,
 }
 
 type (
@@ -77,6 +78,7 @@ func New(l *lexer.Lexer) *Parser {
 	p.registerInfix(token.NOT_EQ, p.parseInfixExpression)
 	p.registerInfix(token.LT, p.parseInfixExpression)
 	p.registerInfix(token.GT, p.parseInfixExpression)
+	p.registerInfix(token.LPAREN, p.parseCallExpression)
 
 	return p
 }
@@ -399,3 +401,33 @@ func (p *Parser) parseFunctionLiteral() ast.Expression {
 
 	return lit
 }
+
+func (p *Parser) parseCallArguments() []ast.Expression {
+	var args []ast.Expression
+
+	if p.peekTokenIs(token.RPAREN) {
+		p.nextToken()
+		return args
+	}
+
+	p.nextToken()
+	args = append(args, p.parseExpression(LOWEST))
+
+	for p.peekTokenIs(token.COMMA) {
+		p.nextToken()
+		p.nextToken()
+		args = append(args, p.parseExpression(LOWEST))
+	}
+
+	if !p.expectPeek(token.RPAREN) {
+		return nil
+	}
+
+	return args
+}
+
+func (p *Parser) parseCallExpression(function ast.Expression) ast.Expression {
+	exp := &ast.CallExpression{Token: p.curToken, Function: function}
+	exp.Arguments = p.parseCallArguments()
+	return exp
+}

parser/parser_test.go

@@ -435,6 +435,18 @@ func TestOperatorPrecedenceParsing(t *testing.T) {
 			"!(true == true)",
 			"(!(true == true))",
 		},
+		{
+			"a + add(b * c) + d",
+			"((a + add((b * c))) + d)",
+		},
+		{
+			"add(a, b, 1, 2 * 3, 4 + 5, add(6, 7 * 8))",
+			"add(a, b, 1, (2 * 3), (4 + 5), add(6, (7 * 8)))",
+		},
+		{
+			"add(a + b + c * d / f + g)",
+			"add((((a + b) + ((c * d) / f)) + g))",
+		},
 	}
 
 	for _, tt := range tests {
@@ -684,3 +696,41 @@ func TestFunctionParameterParsing(t *testing.T) {
 		}
 	}
 }
+
+func TestCallExpressionParsing(t *testing.T) {
+	input := "add(1, 2 * 3, 4 + 5);"
+
+	l := lexer.New(input)
+	p := New(l)
+	program := p.ParseProgram()
+	checkParserErrors(t, p)
+
+	if len(program.Statements) != 1 {
+		t.Fatalf("program.Statements does not contain %d statements. got=%d\n",
+			1, len(program.Statements))
+	}
+
+	stmt, ok := program.Statements[0].(*ast.ExpressionStatement)
+	if !ok {
+		t.Fatalf("stmt is not ast.ExpressionStatement. got=%T",
+			program.Statements[0])
+	}
+
+	exp, ok := stmt.Expression.(*ast.CallExpression)
+	if !ok {
+		t.Fatalf("stmt.Expression is not ast.CallExpression. got=%T",
+			stmt.Expression)
+	}
+
+	if !testIdentifier(t, exp.Function, "add") {
+		return
+	}
+
+	if len(exp.Arguments) != 3 {
+		t.Fatalf("wrong length of arguments. got=%d", len(exp.Arguments))
+	}
+
+	testLiteralExpression(t, exp.Arguments[0], 1)
+	testInfixExpression(t, exp.Arguments[1], 2, "*", 3)
+	testInfixExpression(t, exp.Arguments[2], 4, "+", 5)
+}