diff options
Diffstat (limited to 'libgo/go/math/big/floatconv.go')
| -rw-r--r-- | libgo/go/math/big/floatconv.go | 63 |
1 files changed, 37 insertions, 26 deletions
diff --git a/libgo/go/math/big/floatconv.go b/libgo/go/math/big/floatconv.go index 95d1bf84e24..95e32d3319c 100644 --- a/libgo/go/math/big/floatconv.go +++ b/libgo/go/math/big/floatconv.go @@ -55,7 +55,7 @@ func (z *Float) scan(r io.ByteScanner, base int) (f *Float, b int, err error) { // exponent var exp int64 var ebase int - exp, ebase, err = scanExponent(r, true) + exp, ebase, err = scanExponent(r, true, base == 0) if err != nil { return } @@ -70,8 +70,8 @@ func (z *Float) scan(r io.ByteScanner, base int) (f *Float, b int, err error) { } // len(z.mant) > 0 - // The mantissa may have a decimal point (fcount <= 0) and there - // may be a nonzero exponent exp. The decimal point amounts to a + // The mantissa may have a radix point (fcount <= 0) and there + // may be a nonzero exponent exp. The radix point amounts to a // division by b**(-fcount). An exponent means multiplication by // ebase**exp. Finally, mantissa normalization (shift left) requires // a correcting multiplication by 2**(-shiftcount). Multiplications @@ -85,11 +85,11 @@ func (z *Float) scan(r io.ByteScanner, base int) (f *Float, b int, err error) { exp2 := int64(len(z.mant))*_W - fnorm(z.mant) exp5 := int64(0) - // determine binary or decimal exponent contribution of decimal point + // determine binary or decimal exponent contribution of radix point if fcount < 0 { - // The mantissa has a "decimal" point ddd.dddd; and - // -fcount is the number of digits to the right of '.'. - // Adjust relevant exponent accordingly. + // The mantissa has a radix point ddd.dddd; and + // -fcount is the number of digits to the right + // of '.'. Adjust relevant exponent accordingly. d := int64(fcount) switch b { case 10: @@ -97,6 +97,8 @@ func (z *Float) scan(r io.ByteScanner, base int) (f *Float, b int, err error) { fallthrough // 10**e == 5**e * 2**e case 2: exp2 += d + case 8: + exp2 += d * 3 // octal digits are 3 bits each case 16: exp2 += d * 4 // hexadecimal digits are 4 bits each default: @@ -109,7 +111,7 @@ func (z *Float) scan(r io.ByteScanner, base int) (f *Float, b int, err error) { switch ebase { case 10: exp5 += exp - fallthrough + fallthrough // see fallthrough above case 2: exp2 += exp default: @@ -214,35 +216,44 @@ func (z *Float) pow5(n uint64) *Float { // point number with a mantissa in the given conversion base (the exponent // is always a decimal number), or a string representing an infinite value. // +// For base 0, an underscore character ``_'' may appear between a base +// prefix and an adjacent digit, and between successive digits; such +// underscores do not change the value of the number, or the returned +// digit count. Incorrect placement of underscores is reported as an +// error if there are no other errors. If base != 0, underscores are +// not recognized and thus terminate scanning like any other character +// that is not a valid radix point or digit. +// // 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" ) . -// 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" ) . +// number = [ sign ] ( float | "inf" | "Inf" ) . +// sign = "+" | "-" . +// float = ( mantissa | prefix pmantissa ) [ exponent ] . +// prefix = "0" [ "b" | "B" | "o" | "O" | "x" | "X" ] . +// mantissa = digits "." [ digits ] | digits | "." digits . +// pmantissa = [ "_" ] digits "." [ digits ] | [ "_" ] digits | "." digits . +// exponent = ( "e" | "E" | "p" | "P" ) [ sign ] digits . +// digits = digit { [ "_" ] digit } . +// digit = "0" ... "9" | "a" ... "z" | "A" ... "Z" . // -// The base argument must be 0, 2, 10, or 16. Providing an invalid base +// The base argument must be 0, 2, 8, 10, or 16. Providing an invalid base // argument will lead to a run-time panic. // // For base 0, the number prefix determines the actual base: A prefix of -// "0x" or "0X" selects base 16, and a "0b" or "0B" prefix selects -// base 2; otherwise, the actual base is 10 and no prefix is accepted. -// The octal prefix "0" is not supported (a leading "0" is simply -// considered a "0"). +// ``0b'' or ``0B'' selects base 2, ``0o'' or ``0O'' selects base 8, and +// ``0x'' or ``0X'' selects base 16. Otherwise, the actual base is 10 and +// no prefix is accepted. The octal prefix "0" is not supported (a leading +// "0" is simply considered a "0"). // -// A "p" exponent indicates a binary (rather then decimal) exponent; -// for instance "0x1.fffffffffffffp1023" (using base 0) represents the -// maximum float64 value. For hexadecimal mantissae, the exponent must -// be binary, if present (an "e" or "E" exponent indicator cannot be -// distinguished from a mantissa digit). +// A "p" or "P" exponent indicates a base 2 (rather then base 10) exponent; +// for instance, "0x1.fffffffffffffp1023" (using base 0) represents the +// maximum float64 value. For hexadecimal mantissae, the exponent character +// must be one of 'p' or 'P', if present (an "e" or "E" exponent indicator +// cannot be distinguished from a mantissa digit). // // The returned *Float f is nil and the value of z is valid but not // defined if an error is reported. |