diff options
Diffstat (limited to 'libgo/go/math/big/rat.go')
| -rw-r--r-- | libgo/go/math/big/rat.go | 164 |
1 files changed, 9 insertions, 155 deletions
diff --git a/libgo/go/math/big/rat.go b/libgo/go/math/big/rat.go index c5339fe4431..fb16f18a964 100644 --- a/libgo/go/math/big/rat.go +++ b/libgo/go/math/big/rat.go @@ -11,7 +11,6 @@ import ( "errors" "fmt" "math" - "strings" ) // A Rat represents a quotient a/b of arbitrary precision. @@ -324,14 +323,14 @@ func (z *Rat) SetFrac64(a, b int64) *Rat { // SetInt sets z to x (by making a copy of x) and returns z. func (z *Rat) SetInt(x *Int) *Rat { z.a.Set(x) - z.b.abs = z.b.abs.make(0) + z.b.abs = z.b.abs[:0] return z } // SetInt64 sets z to x and returns z. func (z *Rat) SetInt64(x int64) *Rat { z.a.SetInt64(x) - z.b.abs = z.b.abs.make(0) + z.b.abs = z.b.abs[:0] return z } @@ -370,7 +369,7 @@ func (z *Rat) Inv(x *Rat) *Rat { } b := z.a.abs if b.cmp(natOne) == 0 { - b = b.make(0) // normalize denominator + b = b[:0] // normalize denominator } z.a.abs, z.b.abs = a, b // sign doesn't change return z @@ -386,7 +385,7 @@ func (x *Rat) Sign() int { return x.a.Sign() } -// IsInt returns true if the denominator of x is 1. +// IsInt reports whether the denominator of x is 1. func (x *Rat) IsInt() bool { return len(x.b.abs) == 0 || x.b.abs.cmp(natOne) == 0 } @@ -415,12 +414,12 @@ func (z *Rat) norm() *Rat { case len(z.a.abs) == 0: // z == 0 - normalize sign and denominator z.a.neg = false - z.b.abs = z.b.abs.make(0) + z.b.abs = z.b.abs[:0] case len(z.b.abs) == 0: // z is normalized int - nothing to do case z.b.abs.cmp(natOne) == 0: // z is int - normalize denominator - z.b.abs = z.b.abs.make(0) + z.b.abs = z.b.abs[:0] default: neg := z.a.neg z.a.neg = false @@ -430,7 +429,7 @@ func (z *Rat) norm() *Rat { z.b.abs, _ = z.b.abs.div(nil, z.b.abs, f.abs) if z.b.abs.cmp(natOne) == 0 { // z is int - normalize denominator - z.b.abs = z.b.abs.make(0) + z.b.abs = z.b.abs[:0] } } z.a.neg = neg @@ -512,151 +511,6 @@ func (z *Rat) Quo(x, y *Rat) *Rat { return z.norm() } -func ratTok(ch rune) bool { - return strings.IndexRune("+-/0123456789.eE", ch) >= 0 -} - -// Scan is a support routine for fmt.Scanner. It accepts the formats -// 'e', 'E', 'f', 'F', 'g', 'G', and 'v'. All formats are equivalent. -func (z *Rat) Scan(s fmt.ScanState, ch rune) error { - tok, err := s.Token(true, ratTok) - if err != nil { - return err - } - if strings.IndexRune("efgEFGv", ch) < 0 { - return errors.New("Rat.Scan: invalid verb") - } - if _, ok := z.SetString(string(tok)); !ok { - return errors.New("Rat.Scan: invalid syntax") - } - return nil -} - -// SetString sets z to the value of s and returns z and a boolean indicating -// success. s can be given as a fraction "a/b" or as a floating-point number -// optionally followed by an exponent. If the operation failed, the value of -// z is undefined but the returned value is nil. -func (z *Rat) SetString(s string) (*Rat, bool) { - if len(s) == 0 { - return nil, false - } - - // check for a quotient - sep := strings.Index(s, "/") - if sep >= 0 { - if _, ok := z.a.SetString(s[0:sep], 10); !ok { - return nil, false - } - s = s[sep+1:] - var err error - if z.b.abs, _, err = z.b.abs.scan(strings.NewReader(s), 10); err != nil { - return nil, false - } - if len(z.b.abs) == 0 { - return nil, false - } - return z.norm(), true - } - - // check for a decimal point - sep = strings.Index(s, ".") - // check for an exponent - e := strings.IndexAny(s, "eE") - var exp Int - if e >= 0 { - if e < sep { - // The E must come after the decimal point. - return nil, false - } - if _, ok := exp.SetString(s[e+1:], 10); !ok { - return nil, false - } - s = s[0:e] - } - if sep >= 0 { - s = s[0:sep] + s[sep+1:] - exp.Sub(&exp, NewInt(int64(len(s)-sep))) - } - - if _, ok := z.a.SetString(s, 10); !ok { - return nil, false - } - powTen := nat(nil).expNN(natTen, exp.abs, nil) - if exp.neg { - z.b.abs = powTen - z.norm() - } else { - z.a.abs = z.a.abs.mul(z.a.abs, powTen) - z.b.abs = z.b.abs.make(0) - } - - return z, true -} - -// String returns a string representation of x in the form "a/b" (even if b == 1). -func (x *Rat) String() string { - s := "/1" - if len(x.b.abs) != 0 { - s = "/" + x.b.abs.decimalString() - } - return x.a.String() + s -} - -// RatString returns a string representation of x in the form "a/b" if b != 1, -// and in the form "a" if b == 1. -func (x *Rat) RatString() string { - if x.IsInt() { - return x.a.String() - } - return x.String() -} - -// FloatString returns a string representation of x in decimal form with prec -// digits of precision after the decimal point and the last digit rounded. -func (x *Rat) FloatString(prec int) string { - if x.IsInt() { - s := x.a.String() - if prec > 0 { - s += "." + strings.Repeat("0", prec) - } - return s - } - // x.b.abs != 0 - - q, r := nat(nil).div(nat(nil), x.a.abs, x.b.abs) - - p := natOne - if prec > 0 { - p = nat(nil).expNN(natTen, nat(nil).setUint64(uint64(prec)), nil) - } - - r = r.mul(r, p) - r, r2 := r.div(nat(nil), r, x.b.abs) - - // see if we need to round up - r2 = r2.add(r2, r2) - if x.b.abs.cmp(r2) <= 0 { - r = r.add(r, natOne) - if r.cmp(p) >= 0 { - q = nat(nil).add(q, natOne) - r = nat(nil).sub(r, p) - } - } - - s := q.decimalString() - if x.a.neg { - s = "-" + s - } - - if prec > 0 { - rs := r.decimalString() - leadingZeros := prec - len(rs) - s += "." + strings.Repeat("0", leadingZeros) + rs - } - - return s -} - // Gob codec version. Permits backward-compatible changes to the encoding. const ratGobVersion byte = 1 @@ -667,7 +521,7 @@ func (x *Rat) GobEncode() ([]byte, error) { } buf := make([]byte, 1+4+(len(x.a.abs)+len(x.b.abs))*_S) // extra bytes for version and sign bit (1), and numerator length (4) i := x.b.abs.bytes(buf) - j := x.a.abs.bytes(buf[0:i]) + j := x.a.abs.bytes(buf[:i]) n := i - j if int(uint32(n)) != n { // this should never happen @@ -692,7 +546,7 @@ func (z *Rat) GobDecode(buf []byte) error { } b := buf[0] if b>>1 != ratGobVersion { - return errors.New(fmt.Sprintf("Rat.GobDecode: encoding version %d not supported", b>>1)) + return fmt.Errorf("Rat.GobDecode: encoding version %d not supported", b>>1) } const j = 1 + 4 i := j + binary.BigEndian.Uint32(buf[j-4:j]) |