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big: Improvements to Rat.SetString

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* Allow an exponent part. This is necessary for exp/eval.
* Fix a bug for input that had no numbers after the decimal.
* In Int.SetString, allow a leading + sign.
* In Int.SetString, error if the input is "-" with no number.
* In nat.scan, normalize the resulting nat.

R=gri
CC=golang-dev
https://golang.org/cl/1733045
This commit is contained in:
Evan Shaw 2010-07-09 11:24:31 -07:00 committed by Robert Griesemer
parent 56b3e5d644
commit 2e00bf9877
5 changed files with 61 additions and 27 deletions
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8
src/pkg/big/int.go
View File

@ -347,10 +347,12 @@ func (z *Int) SetString(s string, base int) (*Int, bool) {
return z, false
}
neg := false
if s[0] == '-' {
neg = true
neg := s[0] == '-'
if neg || s[0] == '+' {
s = s[1:]
if len(s) == 0 {
return z, false
}
}
var scanned int

5
src/pkg/big/int_test.go
View File

@ -219,6 +219,7 @@ var stringTests = []stringTest{
stringTest{in: "a", ok: false},
stringTest{in: "z", ok: false},
stringTest{in: "+", ok: false},
stringTest{in: "-", ok: false},
stringTest{in: "0b", ok: false},
stringTest{in: "0x", ok: false},
stringTest{in: "2", base: 2, ok: false},
@ -230,13 +231,17 @@ var stringTests = []stringTest{
stringTest{"0", "0", 0, 0, true},
stringTest{"0", "0", 10, 0, true},
stringTest{"0", "0", 16, 0, true},
stringTest{"+0", "0", 0, 0, true},
stringTest{"-0", "0", 0, 0, true},
stringTest{"10", "10", 0, 10, true},
stringTest{"10", "10", 10, 10, true},
stringTest{"10", "10", 16, 16, true},
stringTest{"-10", "-10", 16, -16, true},
stringTest{"+10", "10", 16, 16, true},
stringTest{"0x10", "16", 0, 16, true},
stringTest{in: "0x10", base: 16, ok: false},
stringTest{"-0x10", "-16", 0, -16, true},
stringTest{"+0x10", "16", 0, 16, true},
stringTest{"00", "0", 0, 0, true},
stringTest{"0", "0", 8, 0, true},
stringTest{"07", "7", 0, 7, true},

6
src/pkg/big/nat.go
View File

@ -103,9 +103,7 @@ func (z nat) setUint64(x uint64) nat {
func (z nat) set(x nat) nat {
z = z.make(len(x))
for i, d := range x {
z[i] = d
}
copy(z, x)
return z
}
@ -666,7 +664,7 @@ func (z nat) scan(s string, base int) (nat, int, int) {
}
}
return z, base, i
return z.norm(), base, i
}

56
src/pkg/big/rat.go
View File

@ -186,26 +186,17 @@ func (z *Rat) Set(x *Rat) *Rat {
// 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 decimal number "a.b".
// If the operation failed, the value of z is undefined.
// 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.
func (z *Rat) SetString(s string) (*Rat, bool) {
if len(s) == 0 {
return z, false
}
// Check for a decimal point
sep := strings.Index(s, ".")
if sep < 0 {
// Check for a quotient
sep = strings.Index(s, "/")
if sep < 0 {
// Just read in the string as an integer
if _, ok := z.a.SetString(s, 10); !ok {
return z, false
}
z.b = z.b.setWord(1)
return z, true
}
// check for a quotient
sep := strings.Index(s, "/")
if sep >= 0 {
if _, ok := z.a.SetString(s[0:sep], 10); !ok {
return z, false
}
@ -214,17 +205,42 @@ func (z *Rat) SetString(s string) (*Rat, bool) {
if z.b, _, n = z.b.scan(s, 10); n != len(s) {
return z, false
}
return z.norm(), true
}
s = s[0:sep] + s[sep+1:]
// 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 z, false
}
if _, ok := exp.SetString(s[e+1:], 10); !ok {
return z, 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 z, false
}
z.b = z.b.expNN(natTen, nat{Word(len(s) - sep)}, nil)
powTen := nat{}.expNN(natTen, exp.abs, nil)
if exp.neg {
z.b = powTen
z.norm()
} else {
z.a.abs = z.a.abs.mul(z.a.abs, powTen)
z.b = z.b.setWord(1)
}
return z.norm(), true
return z, true
}
@ -257,7 +273,7 @@ func (z *Rat) FloatString(prec int) string {
r = r.mul(r, p)
r, r2 := r.div(nat{}, r, z.b)
// See if we need to round up
// see if we need to round up
r2 = r2.mul(r2, natTwo)
if z.b.cmp(r2) <= 0 {
r = r.add(r, natOne)

13
src/pkg/big/rat_test.go
View File

@ -17,6 +17,13 @@ var setStringTests = []setStringTest{
setStringTest{"-0", "0", true},
setStringTest{"1", "1", true},
setStringTest{"-1", "-1", true},
setStringTest{"1.", "1", true},
setStringTest{"1e0", "1", true},
setStringTest{"1.e1", "10", true},
setStringTest{in: "1e", ok: false},
setStringTest{in: "1.e", ok: false},
setStringTest{in: "1e+14e-5", ok: false},
setStringTest{in: "1e4.5", ok: false},
setStringTest{in: "r", ok: false},
setStringTest{in: "a/b", ok: false},
setStringTest{in: "a.b", ok: false},
@ -25,6 +32,12 @@ var setStringTests = []setStringTest{
setStringTest{"2/4", "1/2", true},
setStringTest{".25", "1/4", true},
setStringTest{"-1/5", "-1/5", true},
setStringTest{"8129567.7690E14", "812956776900000000000", true},
setStringTest{"78189e+4", "781890000", true},
setStringTest{"553019.8935e+8", "55301989350000", true},
setStringTest{"98765432109876543210987654321e-10", "98765432109876543210987654321/10000000000", true},
setStringTest{"9877861857500000E-7", "3951144743/4", true},
setStringTest{"2169378.417e-3", "2169378417/1000000", true},
setStringTest{"884243222337379604041632732738665534", "884243222337379604041632732738665534", true},
setStringTest{"53/70893980658822810696", "53/70893980658822810696", true},
setStringTest{"106/141787961317645621392", "53/70893980658822810696", true},