1 files changed, 21 insertions, 3 deletions

diff --git a/libgo/go/math/big/floatconv.go b/libgo/go/math/big/floatconv.go
index a884df6fe1c..95d1bf84e24 100644
--- a/libgo/go/math/big/floatconv.go
+++ b/libgo/go/math/big/floatconv.go
@@ -12,9 +12,13 @@ import (
 	"strings"
 )
 
+var floatZero Float
+
 // SetString sets z to the value of s and returns z and a boolean indicating
 // success. s must be a floating-point number of the same format as accepted
-// by Parse, with base argument 0.
+// by Parse, with base argument 0. The entire string (not just a prefix) must
+// be valid for success. If the operation failed, the value of z is undefined
+// but the returned value is nil.
 func (z *Float) SetString(s string) (*Float, bool) {
 	if f, _, err := z.Parse(s, 0); err == nil {
 		return f, true
@@ -212,17 +216,18 @@ func (z *Float) pow5(n uint64) *Float {
 //
 // It sets z to the (possibly rounded) value of the corresponding floating-
 // point value, and returns z, the actual base b, and an error err, if any.
+// The entire string (not just a prefix) must be consumed for success.
 // If z's precision is 0, it is changed to 64 before rounding takes effect.
 // The number must be of the form:
 //
 //	number   = [ sign ] [ prefix ] mantissa [ exponent ] | infinity .
 //	sign     = "+" | "-" .
-//      prefix   = "0" ( "x" | "X" | "b" | "B" ) .
+//	prefix   = "0" ( "x" | "X" | "b" | "B" ) .
 //	mantissa = digits | digits "." [ digits ] | "." digits .
 //	exponent = ( "E" | "e" | "p" ) [ sign ] digits .
 //	digits   = digit { digit } .
 //	digit    = "0" ... "9" | "a" ... "z" | "A" ... "Z" .
-//      infinity = [ sign ] ( "inf" | "Inf" ) .
+//	infinity = [ sign ] ( "inf" | "Inf" ) .
 //
 // The base argument must be 0, 2, 10, or 16. Providing an invalid base
 // argument will lead to a run-time panic.
@@ -273,3 +278,16 @@ func (z *Float) Parse(s string, base int) (f *Float, b int, err error) {
 func ParseFloat(s string, base int, prec uint, mode RoundingMode) (f *Float, b int, err error) {
 	return new(Float).SetPrec(prec).SetMode(mode).Parse(s, base)
 }
+
+var _ fmt.Scanner = &floatZero // *Float must implement fmt.Scanner
+
+// Scan is a support routine for fmt.Scanner; it sets z to the value of
+// the scanned number. It accepts formats whose verbs are supported by
+// fmt.Scan for floating point values, which are:
+// 'b' (binary), 'e', 'E', 'f', 'F', 'g' and 'G'.
+// Scan doesn't handle ±Inf.
+func (z *Float) Scan(s fmt.ScanState, ch rune) error {
+	s.SkipSpace()
+	_, _, err := z.scan(byteReader{s}, 0)
+	return err
+}