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fraction_test.go
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package fraction_test
import (
"math"
"testing"
"github.com/nethruster/go-fraction"
)
func fatalIfErr(t *testing.T, err error) {
t.Helper()
if err != nil {
t.Fatalf("expected nil error got %v instead", err)
}
}
func compare(t *testing.T, f fraction.Fraction, numerator, denominator int64) {
t.Helper()
if f.Numerator() != numerator {
t.Fatalf("expected numerator value to be %v, got %v", numerator, f.Numerator())
}
if f.Denominator() != denominator {
t.Fatalf("expected denominator value to be %v, got %v", denominator, f.Denominator())
}
}
func approxFloat(t *testing.T, fr fraction.Fraction, expected, precision float64) {
t.Helper()
fl := fr.Float64()
if fl < expected-precision || fl > expected+precision {
t.Fatalf("expected fraction around %v with %v of error, got %v", expected, precision, fl)
}
}
func TestNew(t *testing.T) {
_, err := fraction.New(-3, 5)
fatalIfErr(t, err)
_, err = fraction.New(int32(1), uint16(2))
fatalIfErr(t, err)
_, err = fraction.New(0, 2)
fatalIfErr(t, err)
_, err = fraction.New(1, 0)
if err != fraction.ErrZeroDenominator {
t.Fatalf("expected ErrZeroDenominator, got %v", err)
}
_, err = fraction.New(0, 0)
if err != fraction.ErrZeroDenominator {
t.Fatalf("expected ErrZeroDenominator, got %v", err)
}
}
func TestNewSimplify(t *testing.T) {
f, err := fraction.New(402, 21)
fatalIfErr(t, err)
compare(t, f, 134, 7)
f, err = fraction.New(-10, 20)
fatalIfErr(t, err)
compare(t, f, -1, 2)
f, err = fraction.New(6, -9)
fatalIfErr(t, err)
compare(t, f, -2, 3)
f, err = fraction.New(-44, -11)
fatalIfErr(t, err)
compare(t, f, 4, 1)
f, err = fraction.New(0, 9)
fatalIfErr(t, err)
compare(t, f, 0, 1)
f, err = fraction.New(0, -6)
fatalIfErr(t, err)
compare(t, f, 0, 1)
}
func TestEquals(t *testing.T) {
f1, _ := fraction.New(-19, 27)
f2, _ := fraction.New(57, -81)
f3, _ := fraction.New(-57, -81)
if !f1.Equal(f2) {
t.Fatal("expected both fractions (-19/27) to be equal, got not equal")
}
if f1.Equal(f3) {
t.Fatal("expected fraction -19/27 not to be equal to 19/27, got equal")
}
f1, _ = fraction.New(0, 23)
f2, _ = fraction.New(0, 2)
if !f1.Equal(f2) {
t.Fatal("expected both fractions (0/1) to be equal, got not equal")
}
}
func TestAdd(t *testing.T) {
f1, _ := fraction.New(6, 36)
f2, _ := fraction.New(14, 18)
compare(t, f1.Add(f2), 17, 18)
f1, _ = fraction.New(26, 33)
f2, _ = fraction.New(49, -27)
compare(t, f1.Add(f2), -305, 297)
f1, _ = fraction.New(49, 42)
f2, _ = fraction.New(0, -29)
compare(t, f1.Add(f2), 7, 6)
}
func TestSubtract(t *testing.T) {
f1, _ := fraction.New(6, 36)
f2, _ := fraction.New(14, 18)
compare(t, f1.Subtract(f2), -11, 18)
f1, _ = fraction.New(26, 33)
f2, _ = fraction.New(-49, 27)
compare(t, f1.Subtract(f2), 773, 297)
f1, _ = fraction.New(49, 42)
f2, _ = fraction.New(0, -29)
compare(t, f1.Subtract(f2), 7, 6)
f1, _ = fraction.New(-12, 22)
f2, _ = fraction.New(47, -5)
compare(t, f1.Subtract(f2), 487, 55)
}
func TestMultiply(t *testing.T) {
f1, _ := fraction.New(49, 14)
f2, _ := fraction.New(7, 15)
compare(t, f1.Multiply(f2), 49, 30)
f1, _ = fraction.New(26, 33)
f2, _ = fraction.New(0, 27)
compare(t, f1.Multiply(f2), 0, 1)
f1, _ = fraction.New(48, 9)
f2, _ = fraction.New(6, -16)
compare(t, f1.Multiply(f2), -2, 1)
}
func TestDivide(t *testing.T) {
f1, _ := fraction.New(49, 14)
f2, _ := fraction.New(7, 15)
result, err := f1.Divide(f2)
fatalIfErr(t, err)
compare(t, result, 15, 2)
f1, _ = fraction.New(26, 33)
f2, _ = fraction.New(0, 27)
if _, err = f1.Divide(f2); err != fraction.ErrDivideByZero {
t.Fatalf("expected ErrDivideByZero, got %v", err)
}
f1, _ = fraction.New(48, 9)
f2, _ = fraction.New(6, -16)
result, err = f1.Divide(f2)
fatalIfErr(t, err)
compare(t, result, -128, 9)
}
func TestFloat64(t *testing.T) {
f, _ := fraction.New(49, 14)
if f.Float64() != 3.5 {
t.Fatalf("expected 3.5, got %v", f.Float64())
}
f, _ = fraction.New(0, -27)
if f.Float64() != 0 {
t.Fatalf("expected 0, got %v", f.Float64())
}
f, _ = fraction.New(8, -64)
if f.Float64() != -0.125 {
t.Fatalf("expected -0.125, got %v", f.Float64())
}
}
func TestFromFloat64(t *testing.T) {
f, err := fraction.FromFloat64(0)
fatalIfErr(t, err)
compare(t, f, 0, 1)
f, err = fraction.FromFloat64(-0)
fatalIfErr(t, err)
compare(t, f, 0, 1)
f, err = fraction.FromFloat64(1)
fatalIfErr(t, err)
compare(t, f, 1, 1)
f, err = fraction.FromFloat64(-1)
fatalIfErr(t, err)
compare(t, f, -1, 1)
f, err = fraction.FromFloat64(1.25)
fatalIfErr(t, err)
compare(t, f, 5, 4)
f, err = fraction.FromFloat64(-1.25)
fatalIfErr(t, err)
compare(t, f, -5, 4)
f, err = fraction.FromFloat64(4.5e10)
fatalIfErr(t, err)
compare(t, f, 45000000000, 1)
f, err = fraction.FromFloat64(-4.5e10)
fatalIfErr(t, err)
compare(t, f, -45000000000, 1)
// 4.5e-10 cannot be represented in a float64, the closest representation is
// 2^(-32) * 1.1110111011000111101111010101000100101011010101110010 (base 2), which is
// 4.4999999999999999700744318526239758082585495913008344359695911407470703125 * 10^(-10). The fractions in this
// library cannot represent real numbers with arbitrary precision, so it will approximate the result.
f, err = fraction.FromFloat64(4.5e-10)
fatalIfErr(t, err)
approxFloat(t, f, 4.5e-10, 1e-19)
f, err = fraction.FromFloat64(-4.5e-10)
fatalIfErr(t, err)
approxFloat(t, f, -4.5e-10, 1e-19)
// Max number that float64 can represent that fits in an int64.
// Confusingly, printing this float returns 9223372036854775000, but this is an approximation, because if we do the
// correct conversion based on the binary data following the IEEE 754 standard, we can see that the number that the
// float holds it's 2^62 * 1.1111111111111111111111111111111111111111111111111111 (base 2), which is exactly
// 9223372036854774784.
f, err = fraction.FromFloat64(9223372036854774784)
fatalIfErr(t, err)
compare(t, f, 9223372036854774784, 1)
f, err = fraction.FromFloat64(-9223372036854774784)
fatalIfErr(t, err)
compare(t, f, -9223372036854774784, 1)
f, err = fraction.FromFloat64(math.Pow(2, -62))
fatalIfErr(t, err)
compare(t, f, 1, 1<<62)
f, err = fraction.FromFloat64(math.Pow(2, -62) * (-1))
fatalIfErr(t, err)
compare(t, f, -1, 1<<62)
f, err = fraction.FromFloat64(math.Pow(2, -63))
fatalIfErr(t, err)
compare(t, f, 0, 1)
f, err = fraction.FromFloat64(math.Pow(2, -63) * (-1))
fatalIfErr(t, err)
compare(t, f, 0, 1)
if _, err = fraction.FromFloat64(9223372036854776000); err != fraction.ErrOutOfRange {
t.Fatalf("expected ErrOutOfRange, got %v", err)
}
if _, err = fraction.FromFloat64(-9223372036854776000); err != fraction.ErrOutOfRange {
t.Fatalf("expected ErrOutOfRange, got %v", err)
}
if _, err = fraction.FromFloat64(math.Inf(1)); err != fraction.ErrOutOfRange {
t.Fatalf("expected ErrOutOfRange, got %v", err)
}
if _, err = fraction.FromFloat64(math.Inf(-1)); err != fraction.ErrOutOfRange {
t.Fatalf("expected ErrOutOfRange, got %v", err)
}
if _, err = fraction.FromFloat64(math.NaN()); err != fraction.ErrInvalid {
t.Fatalf("expected ErrInvalid, got %v", err)
}
}