From 67c535fdbaed599629848e034b73a009efcfe91a Mon Sep 17 00:00:00 2001
From: Shulhan <ms@kilabit.info>
Date: Fri, 23 Apr 2021 13:14:36 +0700
Subject: math/big: add method IsZero on Int

The IsZero method will return true if the current i value is zero.
---
 lib/math/big/int.go      |  9 +++++++++
 lib/math/big/int_test.go | 18 ++++++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/lib/math/big/int.go b/lib/math/big/int.go
index c4cb0289..4cbf2632 100644
--- a/lib/math/big/int.go
+++ b/lib/math/big/int.go
@@ -12,6 +12,8 @@ import (
 	"strings"
 )
 
+var intZero = NewInt(0)
+
 //
 // Int extends the standard big.Int package.
 //
@@ -33,6 +35,13 @@ func NewInt(v interface{}) (i *Int) {
 	return i
 }
 
+//
+// IsZero will return true if `i == 0`.
+//
+func (i *Int) IsZero() bool {
+	return i.Cmp(&intZero.Int) == 0
+}
+
 //
 // MarshalJSON implement the json.Marshaler interface and return the output of
 // String method.
diff --git a/lib/math/big/int_test.go b/lib/math/big/int_test.go
index 913aacca..003fcdf1 100644
--- a/lib/math/big/int_test.go
+++ b/lib/math/big/int_test.go
@@ -61,3 +61,21 @@ func TestNewInt(t *testing.T) {
 		test.Assert(t, "NewInt", c.exp, got.String())
 	}
 }
+
+func TestInt_IsZero(t *testing.T) {
+	cases := []struct {
+		in  *Int
+		exp bool
+	}{{
+		in:  NewInt(0),
+		exp: true,
+	}, {
+		in: NewInt(1),
+	}, {
+		in: NewInt(-1),
+	}}
+
+	for _, c := range cases {
+		test.Assert(t, "Int.IsZero", c.in.IsZero(), c.exp)
+	}
+}
-- 
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