math.big: implement decimal .str() for big numbers (#7314)

vlib/math/big/big.v

@@ -1,61 +1,98 @@
 module big
 
 // Wrapper for https://github.com/kokke/tiny-bignum-c
-
 #flag -I @VROOT/thirdparty/bignum
 #flag @VROOT/thirdparty/bignum/bn.o
 #include "bn.h"
-
 [typedef]
 struct C.bn {
 	array [32]u32
 }
 
+// Big unsigned integer number.
 type Number = C.bn
 
-fn C.bignum_init( n &Number )
+fn C.bignum_init(n &Number)
-fn C.bignum_from_int( n &Number, i u64 )
-fn C.bignum_to_int( n &Number ) int
-fn C.bignum_from_string( n &Number, s byteptr, nbytes int)
-fn C.bignum_to_string( n &Number, s byteptr, maxsize int)
 
-fn C.bignum_add( a &Number, b &Number, c &Number) // c = a + b
+fn C.bignum_from_int(n &Number, i u64)
-fn C.bignum_sub( a &Number, b &Number, c &Number) // c = a - b
-fn C.bignum_mul( a &Number, b &Number, c &Number) // c = a * b
-fn C.bignum_div( a &Number, b &Number, c &Number) // c = a / b
-fn C.bignum_mod( a &Number, b &Number, c &Number) // c = a % b
-fn C.bignum_divmod( a &Number, b &Number, c &Number, d &Number)  // c = a/b d=a%b
 
-fn C.bignum_and( a &Number, b &Number, c &Number) // c = a & b
+fn C.bignum_to_int(n &Number) int
-fn C.bignum_or( a &Number, b &Number, c &Number)  // c = a | b
-fn C.bignum_xor( a &Number, b &Number, c &Number) // c = a xor b
-fn C.bignum_lshift( a &Number, b &Number, nbits int) // b = a << nbits
-fn C.bignum_rshift( a &Number, b &Number, nbits int) // b = a >> nbits
 
-fn C.bignum_cmp( a &Number, b &Number) int
+fn C.bignum_from_string(n &Number, s byteptr, nbytes int)
-fn C.bignum_is_zero( a &Number) int
+
+fn C.bignum_to_string(n &Number, s byteptr, maxsize int)
+
+// c = a + b
+fn C.bignum_add(a &Number, b &Number, c &Number)
+
+// c = a - b
+fn C.bignum_sub(a &Number, b &Number, c &Number)
+
+// c = a * b
+fn C.bignum_mul(a &Number, b &Number, c &Number)
+
+// c = a / b
+fn C.bignum_div(a &Number, b &Number, c &Number)
+
+// c = a % b
+fn C.bignum_mod(a &Number, b &Number, c &Number)
+
+// c = a/b d=a%b
+fn C.bignum_divmod(a &Number, b &Number, c &Number, d &Number)
+
+// c = a & b
+fn C.bignum_and(a &Number, b &Number, c &Number)
+
+// c = a | b
+fn C.bignum_or(a &Number, b &Number, c &Number)
+
+// c = a xor b
+fn C.bignum_xor(a &Number, b &Number, c &Number)
+
+// b = a << nbits
+fn C.bignum_lshift(a &Number, b &Number, nbits int)
+
+// b = a >> nbits
+fn C.bignum_rshift(a &Number, b &Number, nbits int)
+
+fn C.bignum_cmp(a &Number, b &Number) int
+
+fn C.bignum_is_zero(a &Number) int
+
+// n++
 fn C.bignum_inc(n &Number)
-fn C.bignum_dec(n &Number)
-fn C.bignum_pow( a &Number, b &Number, c &Number) // c = a ^ b
-fn C.bignum_isqrt( a &Number, b &Number) // b = integer_square_root_of(a)
-fn C.bignum_assign( dst &Number, src &Number) // copy src number to dst number
 
-////////////////////////////////////////////////////////////
+// n--
+fn C.bignum_dec(n &Number)
+
+// c = a ^ b
+fn C.bignum_pow(a &Number, b &Number, c &Number)
+
+// b = integer_square_root_of(a)
+fn C.bignum_isqrt(a &Number, b &Number)
+
+// copy src number to dst number
+fn C.bignum_assign(dst &Number, src &Number)
+
+// //////////////////////////////////////////////////////////
 // conversion actions to/from big numbers:
 pub fn new() Number {
 	return Number{}
 }
+
 pub fn from_int(i int) Number {
 	n := Number{}
-	C.bignum_from_int( &n, i)
+	C.bignum_from_int(&n, i)
 	return n
 }
 
 pub fn from_u64(u u64) Number {
 	n := Number{}
-	C.bignum_from_int( &n, u)
+	C.bignum_from_int(&n, u)
 	return n
 }
+
+// Converts a hex string to big.Number.
 pub fn from_string(s string) Number {
 	n := Number{}
 	C.bignum_from_string(&n, s.str, s.len)
@@ -67,119 +104,147 @@ pub fn (n Number) int() int {
 	return r
 }
 
+const (
+	ten = from_int(10)
+)
+
+// Decimal representation for the big unsigned integer number n.
 pub fn (n Number) str() string {
-	// TODO: return a decimal representation of the bignumber n.
+	if n.is_zero() {
-	// A decimal representation will be easier to use in the repl
+		return '0'
-	// but will be slower to calculate. Also, it is not implemented
+	}
-	// in the bn library.
+	mut digits := []byte{}
-	return 'Number (in hex): ' + n.hexstr()
+	mut x := n.clone()
+	div := Number{}
+	for !x.is_zero() {
+		mod := divmod(&x, &ten, &div)
+		digits << byte(mod.int()) + `0`
+		x = div
+	}
+	return digits.reverse().bytestr()
 }
 
 pub fn (n Number) hexstr() string {
 	mut buf := [8192]byte{}
-	C.bignum_to_string( &n, buf, 8192)
+	C.bignum_to_string(&n, buf, 8192)
 	// NB: bignum_to_string , returns the HEXADECIMAL representation of the bignum n
-	s := tos_clone( buf )
+	s := tos_clone(buf)
-	if s.len == 0 { return '0' }
+	if s.len == 0 {
+		return '0'
+	}
 	return s
 }
-////////////////////////////////////////////////////////////
+
+// //////////////////////////////////////////////////////////
 // overloaded ops for the numbers:
-pub fn (a Number) + (b Number) Number {
+pub fn (a Number) +(b Number) Number {
 	c := Number{}
 	C.bignum_add(&a, &b, &c)
 	return c
 }
 
-pub fn (a Number) - (b Number) Number {
+pub fn (a Number) -(b Number) Number {
 	c := Number{}
 	C.bignum_sub(&a, &b, &c)
 	return c
 }
 
-pub fn (a Number) * (b Number) Number {
+pub fn (a Number) *(b Number) Number {
 	c := Number{}
 	C.bignum_mul(&a, &b, &c)
 	return c
 }
 
-pub fn (a Number) / (b Number) Number {
+pub fn (a Number) /(b Number) Number {
 	c := Number{}
 	C.bignum_div(&a, &b, &c)
 	return c
 }
 
-pub fn (a Number) % (b Number) Number {
+pub fn (a Number) %(b Number) Number {
 	c := Number{}
 	C.bignum_mod(&a, &b, &c)
 	return c
 }
 
-pub fn divmod( a &Number, b &Number, c &Number) Number {
+pub fn divmod(a &Number, b &Number, c &Number) Number {
 	d := Number{}
-	C.bignum_divmod( a, b, c, &d)
+	C.bignum_divmod(a, b, c, &d)
 	return d
 }
-////////////////////////////////////////////////////////////
+
+// //////////////////////////////////////////////////////////
 pub fn cmp(a Number, b Number) int {
-	return C.bignum_cmp(&a,&b)
+	return C.bignum_cmp(&a, &b)
 }
+
 pub fn (a Number) is_zero() bool {
 	return C.bignum_is_zero(&a) != 0
 }
+
 pub fn (mut a Number) inc() {
 	C.bignum_inc(a)
 }
+
 pub fn (mut a Number) dec() {
 	C.bignum_dec(a)
 }
+
 pub fn pow(a Number, b Number) Number {
 	c := Number{}
-	C.bignum_pow(&a,&b,&c)
+	C.bignum_pow(&a, &b, &c)
 	return c
 }
+
 pub fn (a Number) isqrt() Number {
 	b := Number{}
-	C.bignum_isqrt(&a,&b)
+	C.bignum_isqrt(&a, &b)
 	return b
 }
-////////////////////////////////////////////////////////////
+
+// //////////////////////////////////////////////////////////
 pub fn b_and(a Number, b Number) Number {
 	c := Number{}
-	C.bignum_and(&a,&b,&c)
+	C.bignum_and(&a, &b, &c)
 	return c
 }
+
 pub fn b_or(a Number, b Number) Number {
 	c := Number{}
-	C.bignum_or(&a,&b,&c)
+	C.bignum_or(&a, &b, &c)
 	return c
 }
+
 pub fn b_xor(a Number, b Number) Number {
 	c := Number{}
-	C.bignum_xor(&a,&b,&c)
+	C.bignum_xor(&a, &b, &c)
 	return c
 }
+
 pub fn (a Number) lshift(nbits int) Number {
 	b := Number{}
-	C.bignum_lshift(&a,&b,nbits)
+	C.bignum_lshift(&a, &b, nbits)
 	return b
 }
+
 pub fn (a Number) rshift(nbits int) Number {
 	b := Number{}
-	C.bignum_rshift(&a,&b,nbits)
+	C.bignum_rshift(&a, &b, nbits)
 	return b
 }
+
 pub fn (a Number) clone() Number {
 	b := Number{}
-	C.bignum_assign(&b,&a)
+	C.bignum_assign(&b, &a)
 	return b
 }
-////////////////////////////////////////////////////////////
+
+// //////////////////////////////////////////////////////////
 pub fn factorial(nn Number) Number {
 	mut n := nn.clone()
 	mut a := nn.clone()
 	n.dec()
-	mut i:=1
+	mut i := 1
 	for !n.is_zero() {
 		res := a * n
 		n.dec()
@@ -190,5 +255,5 @@ pub fn factorial(nn Number) Number {
 }
 
 pub fn fact(n int) Number {
-	return factorial( from_int(n) )
+	return factorial(from_int(n))
 }

vlib/math/big/big_test.v

@@ -1,12 +1,12 @@
 import big
 
-fn test_new_big(){
+fn test_new_big() {
 	n := big.new()
-	assert sizeof( big.Number ) == 128
+	assert sizeof(big.Number) == 128
 	assert n.hexstr() == '0'
 }
 
-fn test_from_int(){
+fn test_from_int() {
 	assert big.from_int(255).hexstr() == 'ff'
 	assert big.from_int(127).hexstr() == '7f'
 	assert big.from_int(1024).hexstr() == '400'
@@ -14,7 +14,7 @@ fn test_from_int(){
 	assert big.from_int(-1).hexstr() == 'ffffffffffffffff'
 }
 
-fn test_from_u64(){
+fn test_from_u64() {
 	assert big.from_u64(255).hexstr() == 'ff'
 	assert big.from_u64(127).hexstr() == '7f'
 	assert big.from_u64(1024).hexstr() == '400'
@@ -23,7 +23,7 @@ fn test_from_u64(){
 	assert big.from_u64(-1).hexstr() == 'ffffffffffffffff'
 }
 
-fn test_plus(){
+fn test_plus() {
 	a := big.from_u64(2)
 	b := big.from_u64(3)
 	c := a + b
@@ -31,7 +31,7 @@ fn test_plus(){
 	assert (big.from_u64(1024) + big.from_u64(1024)).hexstr() == '800'
 }
 
-fn test_minus(){
+fn test_minus() {
 	a := big.from_u64(2)
 	b := big.from_u64(3)
 	c := b - a
@@ -41,20 +41,20 @@ fn test_minus(){
 	assert ee.hexstr() == '0'
 }
 
-fn test_divide(){
+fn test_divide() {
 	a := big.from_u64(2)
 	b := big.from_u64(3)
 	c := b / a
 	assert c.hexstr() == '1'
-	assert (b % a ).hexstr() == '1'
+	assert (b % a).hexstr() == '1'
 	e := big.from_u64(1024) // dec(1024) == hex(0x400)
 	ee := e / e
 	assert ee.hexstr() == '1'
 	assert (e / a).hexstr() == '200'
-	assert (e / (a*a)).hexstr() == '100'
+	assert (e / (a * a)).hexstr() == '100'
 }
 
-fn test_multiply(){
+fn test_multiply() {
 	a := big.from_u64(2)
 	b := big.from_u64(3)
 	c := b * a
@@ -64,23 +64,35 @@ fn test_multiply(){
 	e4 := e2 * e2
 	e8 := e2 * e2 * e2 * e2
 	e9 := e8 + big.from_u64(1)
-	d  := ((e9 * e9) + b) * c
+	d := ((e9 * e9) + b) * c
 	assert e4.hexstr() == '10000000000'
 	assert e8.hexstr() == '100000000000000000000'
 	assert e9.hexstr() == '100000000000000000001'
 	assert d.hexstr() == '60000000000000000000c00000000000000000018'
 }
 
-fn test_mod(){
+fn test_mod() {
-	assert (big.from_u64(13) % big.from_u64(10) ).int() == 3
+	assert (big.from_u64(13) % big.from_u64(10)).int() == 3
-	assert (big.from_u64(13) % big.from_u64(9) ).int()  == 4
+	assert (big.from_u64(13) % big.from_u64(9)).int() == 4
-	assert (big.from_u64(7) % big.from_u64(5) ).int() == 2
+	assert (big.from_u64(7) % big.from_u64(5)).int() == 2
 }
 
+fn test_str() {
+	assert big.from_u64(255).str() == '255'
+	assert big.from_u64(127).str() == '127'
+	assert big.from_u64(1024).str() == '1024'
+	assert big.from_u64(4294967295).str() == '4294967295'
+	assert big.from_u64(4398046511104).str() == '4398046511104'
+	assert big.from_int(4294967295).str() == '18446744073709551615'
+	assert big.from_int(-1).str() == '18446744073709551615'
+	assert big.from_string('e'.repeat(80)).str() ==
+		'1993587900192849410235353592424915306962524220866209251950572167300738410728597846688097947807470'
+}
 
-fn test_factorial(){
+fn test_factorial() {
-	f5 := big.factorial( big.from_u64(5) )
+	f5 := big.factorial(big.from_u64(5))
 	assert f5.hexstr() == '78'
-	f100 := big.factorial( big.from_u64(100) )
+	f100 := big.factorial(big.from_u64(100))
-	assert f100.hexstr() == '1b30964ec395dc24069528d54bbda40d16e966ef9a70eb21b5b2943a321cdf10391745570cca9420c6ecb3b72ed2ee8b02ea2735c61a000000000000000000000000'
+	assert f100.hexstr() ==
+		'1b30964ec395dc24069528d54bbda40d16e966ef9a70eb21b5b2943a321cdf10391745570cca9420c6ecb3b72ed2ee8b02ea2735c61a000000000000000000000000'
 }