Refactor/gkr test vectors (#425)

* feat: smallRational.BigInt()

* refactor: simpler ElementToInterface

internal/generator/gkr/test_vectors/single_mimc_gate_four_instances.json

@@ -45,21 +45,21 @@
 					-32640,
 					-2239484,
 					-29360128,
-					"-200000010",
-					"-931628672",
-					"-3373267120",
-					"-10200858624",
-					"-26939400158"
+					-200000010,
+					-931628672,
+					-3373267120,
+					-10200858624,
+					-26939400158
 				],
 				[
 					-81920,
 					-41943040,
-					"-1254113280",
-					"-13421772800",
-					"-83200000000",
-					"-366917713920",
-					"-1281828208640",
-					"-3779571220480"
+					-1254113280,
+					-13421772800,
+					-83200000000,
+					-366917713920,
+					-1281828208640,
+					-3779571220480
 				]
 			]
 		}

internal/generator/gkr/test_vectors/single_mimc_gate_two_instances.json

@@ -43,7 +43,7 @@
 					-10706059,
 					-33554432,
 					-90876411,
-					"-220000000"
+					-220000000
 				]
 			]
 		}

internal/generator/test_vector_utils/small_rational/small-rational.go

@@ -49,6 +49,11 @@ func (z *SmallRational) simplify() {
 		}
 	}
 
+	if bigDivides(&den, &num) {
+		num.Div(&num, &den)
+		den.SetInt64(1)
+	}
+
 	z.numerator = num
 	z.denominator = den
 
@@ -371,8 +376,19 @@ func bytesToBigIntSigned(src []byte) big.Int {
 	return res
 }
 
-func (z *SmallRational) BigInt(*big.Int) *big.Int {
-	panic("not implemented")
+// BigInt returns sets dst to the value of z if it is an integer.
+// if z is not an integer, nil is returned.
+// if the given dst is nil, the address of the numerator is returned.
+// if the given dst is non-nil, it is returned.
+func (z *SmallRational) BigInt(dst *big.Int) *big.Int {
+	if z.denominator.Cmp(big.NewInt(1)) != 0 {
+		return nil
+	}
+	if dst == nil {
+		return &z.numerator
+	}
+	dst.Set(&z.numerator)
+	return dst
 }
 
 func (z *SmallRational) SetBytes(b []byte) {

internal/generator/test_vector_utils/small_rational/small_rational_test.go

@@ -2,9 +2,15 @@ package small_rational
 
 import (
 	"github.com/stretchr/testify/assert"
+	"math/big"
 	"testing"
 )
 
+func TestBigDivides(t *testing.T) {
+	assert.True(t, bigDivides(big.NewInt(-1), big.NewInt(4)))
+	assert.False(t, bigDivides(big.NewInt(-3), big.NewInt(4)))
+}
+
 func TestCmp(t *testing.T) {
 
 	cases := make([]SmallRational, 36)

internal/generator/test_vector_utils/template/test_vector_utils.go.tmpl

@@ -3,10 +3,8 @@ import (
 	"{{.FieldPackagePath}}"
 	"{{.FieldPackagePath}}/polynomial"
 	"hash"
-	"strings"
-	"strconv"
-	"reflect"
 	"reflect"
+	{{if eq .ElementType "fr.Element"}}"strings"{{- end}}
 )
 
 func ToElement(i int64) *{{.ElementType}} {
@@ -185,15 +183,10 @@ func PolynomialSliceEquals(a []polynomial.Polynomial, b []polynomial.Polynomial)
 }
 
 func ElementToInterface(x *{{.ElementType}}) interface{} {
-	text := x.Text(10)
-	if len(text) < 10 && !strings.Contains(text, "/") {
-		if i, err := strconv.Atoi(text); err != nil {
-			panic(err.Error())
-		} else {
-			return i
-		}
+	if i := x.BigInt(nil); i != nil {
+		return i
 	}
-	return text
+	return x.Text(10)
 }
 
 func ElementSliceToInterfaceSlice(x interface{}) []interface{} {