From adc91a1d6b765f0d15cc2b2fd57775f51afb3125 Mon Sep 17 00:00:00 2001
From: Flipez <code@brauser.io>
Date: Thu, 3 Feb 2022 21:26:04 +0100
Subject: [PATCH] add modulo

Signed-off-by: Flipez <code@brauser.io>
---
 evaluator/evaluator_test.go | 2 ++
 evaluator/infix.go          | 5 +++++
 lexer/lexer.go              | 3 +++
 lexer/lexer_test.go         | 5 +++++
 parser/parser.go            | 3 +++
 token/token.go              | 1 +
 6 files changed, 19 insertions(+)

diff --git a/evaluator/evaluator_test.go b/evaluator/evaluator_test.go
index d098522..6708f8d 100644
--- a/evaluator/evaluator_test.go
+++ b/evaluator/evaluator_test.go
@@ -30,6 +30,8 @@ func TestEvalIntegerExpression(t *testing.T) {
 		{"3 * (3 * 3) + 10", 37},
 		{"(5 + 10 * 2 + 15 / 3) * 2 + -10", 50},
 		{"5 ➕ 5 ➕ 5 ➕ 5 - 10", 10},
+		{"5 % 5", 0},
+		{"5 %  4", 1},
 	}
 
 	for _, tt := range tests {
diff --git a/evaluator/infix.go b/evaluator/infix.go
index 04bfbd5..f1f1f11 100644
--- a/evaluator/infix.go
+++ b/evaluator/infix.go
@@ -22,6 +22,11 @@ func evalIntegerInfix(operator string, left, right object.Object) object.Object
 			return object.NewErrorFormat("devision by zero not allowed")
 		}
 		return object.NewInteger(leftVal / rightVal)
+	case "%":
+		if rightVal == 0 {
+			return object.NewErrorFormat("devision by zero not allowed")
+		}
+		return object.NewInteger(leftVal % rightVal)
 	case "<":
 		return nativeBoolToBooleanObject(leftVal < rightVal)
 	case "<=":
diff --git a/lexer/lexer.go b/lexer/lexer.go
index deb39ac..a25bb3b 100644
--- a/lexer/lexer.go
+++ b/lexer/lexer.go
@@ -78,6 +78,9 @@ func (l *Lexer) NextToken() token.Token {
 	case '*':
 		tok.Type = token.ASTERISK
 		tok.Literal = string(l.ch)
+	case '%':
+		tok.Type = token.PERCENT
+		tok.Literal = string(l.ch)
 	case '<':
 		if l.peekChar() == '=' {
 			ch := l.ch
diff --git a/lexer/lexer_test.go b/lexer/lexer_test.go
index d9d10cf..f52eb32 100644
--- a/lexer/lexer_test.go
+++ b/lexer/lexer_test.go
@@ -32,6 +32,7 @@ func TestNextToken(t *testing.T) {
 	{"foo": "bar"}
 
 	5 <= 10 >= 5;
+	4 % 3;
 	`
 
 	tests := []struct {
@@ -126,6 +127,10 @@ func TestNextToken(t *testing.T) {
 		{token.GT_EQ, ">="},
 		{token.INT, "5"},
 		{token.SEMICOLON, ";"},
+		{token.INT, "4"},
+		{token.PERCENT, "%"},
+		{token.INT, "3"},
+		{token.SEMICOLON, ";"},
 		{token.EOF, ""},
 	}
 
diff --git a/parser/parser.go b/parser/parser.go
index f0a7383..bb0c0fa 100644
--- a/parser/parser.go
+++ b/parser/parser.go
@@ -16,6 +16,7 @@ const (
 	LESSGREATER // > or <
 	SUM         // +
 	PRODUCT     // *
+	MODULO      // %
 	PREFIX      // -X or !X
 	CALL        // myFcuntion(X)
 	INDEX       // array[index]
@@ -33,6 +34,7 @@ var precedences = map[token.TokenType]int{
 	token.MINUS:    SUM,
 	token.SLASH:    PRODUCT,
 	token.ASTERISK: PRODUCT,
+	token.PERCENT:  MODULO,
 	token.LPAREN:   CALL,
 	token.PERIOD:   CALL,
 	token.LBRACKET: INDEX,
@@ -87,6 +89,7 @@ func New(l *lexer.Lexer, imports map[string]struct{}) *Parser {
 	p.registerInfix(token.MINUS, p.parseInfix)
 	p.registerInfix(token.SLASH, p.parseInfix)
 	p.registerInfix(token.ASTERISK, p.parseInfix)
+	p.registerInfix(token.PERCENT, p.parseInfix)
 	p.registerInfix(token.EQ, p.parseInfix)
 	p.registerInfix(token.NOT_EQ, p.parseInfix)
 	p.registerInfix(token.PERIOD, p.parseMethodCall)
diff --git a/token/token.go b/token/token.go
index 63f5e42..f7ec54d 100644
--- a/token/token.go
+++ b/token/token.go
@@ -28,6 +28,7 @@ const (
 	BANG     = "!"
 	ASTERISK = "*"
 	SLASH    = "/"
+	PERCENT  = "%"
 
 	LT    = "<"
 	LT_EQ = "<="