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Code Releases Activity

- bug fixes, cleanups

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- integer string conversion

R=r
OCL=17923
CL=17923
This commit is contained in:
Robert Griesemer 2008-10-27 17:57:31 -07:00
parent 2e777b44b8
commit 1daad03545
1 changed files with 34 additions and 26 deletions
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60
usr/gri/bignum/bignum.go
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@ -20,7 +20,8 @@ type Word uint32
const N = 4;
const L = 28; // = sizeof(Word) * 8
const M = 1 << L - 1;
const B = 1 << L;
const M = B - 1;
// TODO replace this with a Go built-in assert
@ -31,6 +32,11 @@ func ASSERT(p bool) {
}
func IsSmall(x Word) bool {
return x < 1 << N;
}
func Update(x Word) (Word, Word) {
return x & M, x >> L;
}
@ -88,8 +94,7 @@ func (x *Natural) Sub (y *Natural) *Natural {
// Computes x = x*a + c (in place) for "small" a's.
func (x* Natural) Mul1Add(a, c Word) *Natural {
ASSERT(0 <= a && a < 1 << N);
ASSERT(0 <= c && c < 1 << N);
ASSERT(IsSmall(a) && IsSmall(c));
if (x.IsZero() || a == 0) && c == 0 {
return NatZero;
}
@ -118,10 +123,10 @@ func Mul1(x, y Word) (z Word, c Word) {
y1 := y >> L2;
z10 := x0*y0;
z21 := x1*y0 + x0*y1 + (z10 >> L2);
z21 := x1*y0 + x0*y1 + z10 >> L2;
cc := x1*y1 + (z21 >> L2);
zz := ((z21 & M2) << L2) | (z10 & M2);
cc := x1*y1 + z21 >> L2;
zz := z21 & M2 << L2 | z10 & M2;
return zz, cc
}
@ -158,7 +163,7 @@ func (x *Natural) Mul (y *Natural) *Natural {
k++;
}
if c != 0 {
z[k] = Word(c);
z[k] = c;
k++;
}
}
@ -235,7 +240,7 @@ func (x *Natural) Or (y *Natural) *Natural {
xl := len(x);
yl := len(y);
if xl < yl {
return y.And(x);
return y.Or(x);
}
ASSERT(xl >= yl);
z := new(Natural, xl);
@ -252,7 +257,7 @@ func (x *Natural) Xor (y *Natural) *Natural {
xl := len(x);
yl := len(y);
if xl < yl {
return y.And(x);
return y.Xor(x);
}
ASSERT(xl >= yl);
z := new(Natural, xl);
@ -279,29 +284,18 @@ func Copy(x *Natural) *Natural {
}
// Computes x = x div d (in place) for "small" d's. Returns x mod d.
// Computes x = x div d (in place) for "small" d's. Returns updated x, x mod d.
func (x *Natural) Mod1 (d Word) (*Natural, Word) {
ASSERT(0 < d && d < (1 << N));
ASSERT(IsSmall(d));
xl := len(x);
c := Word(0);
i := xl;
for i > 0 {
i--;
for i := xl - 1; i >= 0; i-- {
c = c << L + x[i];
q := c / d;
x[i] = q;
//x[i] = c / d; // BUG
c = c % d;
x[i], c = c / d, c %d;
}
if xl > 0 && x[xl - 1] == 0 {
x = x[0 : xl - 1];
if xl - 1 == 0 && len(x) != 0 {
panic();
}
}
return x, c;
@ -337,7 +331,7 @@ export func NatFromWord(x Word) *Natural {
switch {
case x == 0:
z = NatZero;
case x < 2 << L:
case x < B:
z = new(Natural, 1);
z[0] = x;
return z;
@ -456,6 +450,20 @@ func (x *Integer) Cmp (y *Integer) int {
}
func (x *Integer) String() string {
if x.mant.IsZero() {
return "0";
}
var s string;
if x.sign {
s = "-" + x.mant.String();
} else {
s = x.mant.String();
}
return s;
}
export func IntFromString(s string) *Integer {
// get sign, if any
sign := false;