big: Improvements to Rat.SetString
* 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
diff --git a/src/pkg/big/int.go b/src/pkg/big/int.go
index 873d5b5..f16c0d9 100755
--- a/src/pkg/big/int.go
+++ b/src/pkg/big/int.go
@@ -347,10 +347,12 @@
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
diff --git a/src/pkg/big/int_test.go b/src/pkg/big/int_test.go
index 269c814..82b5417 100755
--- a/src/pkg/big/int_test.go
+++ b/src/pkg/big/int_test.go
@@ -219,6 +219,7 @@
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 @@
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},
diff --git a/src/pkg/big/nat.go b/src/pkg/big/nat.go
index dc2e6be..72d9f05 100755
--- a/src/pkg/big/nat.go
+++ b/src/pkg/big/nat.go
@@ -103,9 +103,7 @@
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 @@
}
}
- return z, base, i
+ return z.norm(), base, i
}
diff --git a/src/pkg/big/rat.go b/src/pkg/big/rat.go
index ddd858d..c465ab8 100644
--- a/src/pkg/big/rat.go
+++ b/src/pkg/big/rat.go
@@ -186,26 +186,17 @@
// 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 @@
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 @@
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)
diff --git a/src/pkg/big/rat_test.go b/src/pkg/big/rat_test.go
index 2379cc0..c74ec85 100644
--- a/src/pkg/big/rat_test.go
+++ b/src/pkg/big/rat_test.go
@@ -17,6 +17,13 @@
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 @@
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},
