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https://github.com/golang/go
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math/big: use stringer for enum String() methods
Change-Id: Ide0615542d67b7d81bf6c56aab550e142a8789f7 Reviewed-on: https://go-review.googlesource.com/6682 Reviewed-by: Alan Donovan <adonovan@google.com>
This commit is contained in:
parent
0a8a625848
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16
src/math/big/accuracy_string.go
Normal file
16
src/math/big/accuracy_string.go
Normal file
@ -0,0 +1,16 @@
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// generated by stringer -type=Accuracy; DO NOT EDIT
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package big
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import "fmt"
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const _Accuracy_name = "ExactBelowAboveUndef"
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var _Accuracy_index = [...]uint8{0, 5, 10, 15, 20}
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func (i Accuracy) String() string {
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if i < 0 || i+1 >= Accuracy(len(_Accuracy_index)) {
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return fmt.Sprintf("Accuracy(%d)", i)
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}
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return _Accuracy_name[_Accuracy_index[i]:_Accuracy_index[i+1]]
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}
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@ -18,15 +18,15 @@ import (
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const debugFloat = true // enable for debugging
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// A nonzero Float represents a multi-precision floating point number
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// A nonzero finite Float represents a multi-precision floating point number
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//
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// sign × mantissa × 2**exponent
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//
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// with 0.5 <= mantissa < 1.0, and MinExp <= exponent <= MaxExp.
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// A Float may also be +0, -0, +Inf, -Inf, or NaN.
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// A Float may also be zero (+0, -0), infinite (+Inf, -Inf) or
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// not-a-number (NaN).
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//
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// Each Float value also has a precision, rounding mode, and accuracy.
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//
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// The precision is the maximum number of mantissa bits available to
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// represent the value. The rounding mode specifies how a result should
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// be rounded to fit into the mantissa bits, and accuracy describes the
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@ -46,21 +46,20 @@ const debugFloat = true // enable for debugging
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//
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// By setting the desired precision to 24 or 53 and using matching rounding
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// mode (typically ToNearestEven), Float operations produce the same results
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// as the corresponding float32 or float64 IEEE-754 arithmetic for normalized
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// operands (including +0 and -0). Exponent underflow and overflow lead to a
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// 0 or an Infinity for different values than IEEE-754 because Float exponents
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// hace a much larger range.
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// as the corresponding float32 or float64 IEEE-754 arithmetic. Exponent
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// underflow and overflow lead to a 0 or an Infinity for different values
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// than IEEE-754 because Float exponents have a much larger range.
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//
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// The zero (uninitialized) value for a Float is ready to use and represents
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// the number +0.0 exactly, with precision 0 and rounding mode ToNearestEven.
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//
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type Float struct {
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prec uint32
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mode RoundingMode
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acc Accuracy
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neg bool
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mant nat
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exp int32
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prec uint32
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}
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// Internal representation: The mantissa bits x.mant of a Float x are stored
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@ -81,38 +80,10 @@ const (
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MaxPrec = math.MaxUint32 // largest (theoretically) supported precision; likely memory-limited
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)
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// Accuracy describes the rounding error produced by the most recent
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// operation that generated a Float value, relative to the exact value.
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// The accuracy may be Undef for operations on and resulting in
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// NaNs since they are neither Below nor Above any other value.
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type Accuracy int8
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// Constants describing the Accuracy of a Float.
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const (
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Exact Accuracy = 0
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Below Accuracy = 1 << 0
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Above Accuracy = 1 << 1
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Undef Accuracy = Below | Above
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)
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func (a Accuracy) String() string {
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switch a {
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case Exact:
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return "exact"
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case Below:
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return "below"
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case Above:
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return "above"
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case Undef:
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return "undef"
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}
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panic(fmt.Sprintf("unknown accuracy %d", a))
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}
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// RoundingMode determines how a Float value is rounded to the
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// desired precision. Rounding may change the Float value; the
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// rounding error is described by the Float's Accuracy.
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type RoundingMode uint8
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type RoundingMode byte
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// The following rounding modes are supported.
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const (
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@ -124,23 +95,23 @@ const (
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ToPositiveInf // == IEEE 754-2008 roundTowardPositive
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)
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func (mode RoundingMode) String() string {
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switch mode {
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case ToNearestEven:
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return "ToNearestEven"
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case ToNearestAway:
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return "ToNearestAway"
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case ToZero:
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return "ToZero"
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case AwayFromZero:
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return "AwayFromZero"
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case ToNegativeInf:
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return "ToNegativeInf"
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case ToPositiveInf:
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return "ToPositiveInf"
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}
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panic("unreachable")
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}
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//go:generate stringer -type=RoundingMode
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// Accuracy describes the rounding error produced by the most recent
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// operation that generated a Float value, relative to the exact value.
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// The accuracy is Undef for operations on and resulting in NaNs since
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// they are neither Below nor Above any other value.
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type Accuracy byte
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// Constants describing the Accuracy of a Float.
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const (
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Exact Accuracy = 0
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Below Accuracy = 1 << 0
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Above Accuracy = 1 << 1
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Undef Accuracy = Below | Above
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)
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//go:generate stringer -type=Accuracy
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// SetPrec sets z's precision to prec and returns the (possibly) rounded
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// value of z. Rounding occurs according to z's rounding mode if the mantissa
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@ -179,9 +150,10 @@ func (z *Float) SetPrec(prec uint) *Float {
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// SetMode sets z's rounding mode to mode and returns an exact z.
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// z remains unchanged otherwise.
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// z.SetMode(z.Mode()) is a cheap way to set z's accuracy to Exact.
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func (z *Float) SetMode(mode RoundingMode) *Float {
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z.acc = Exact // TODO(gri) should we not do this? what's the general rule for setting accuracy?
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z.mode = mode
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z.acc = Exact
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return z
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}
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@ -198,16 +170,16 @@ func (x *Float) MinPrec() uint {
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return uint(len(x.mant))*_W - x.mant.trailingZeroBits()
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}
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// Acc returns the accuracy of x produced by the most recent operation.
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func (x *Float) Acc() Accuracy {
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return x.acc
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}
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// Mode returns the rounding mode of x.
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func (x *Float) Mode() RoundingMode {
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return x.mode
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}
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// Acc returns the accuracy of x produced by the most recent operation.
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func (x *Float) Acc() Accuracy {
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return x.acc
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}
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// Sign returns:
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//
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// -1 if x < 0
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@ -288,6 +260,33 @@ func (z *Float) SetMantExp(mant *Float, exp int) *Float {
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return z
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}
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// IsNeg reports whether x is negative.
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// A NaN is not negative.
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func (x *Float) IsNeg() bool {
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return x.neg && x.exp != nanExp
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}
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// IsZero reports whether x is a +0 or -0.
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func (x *Float) IsZero() bool {
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return len(x.mant) == 0 && x.exp == 0
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}
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// IsFinite reports whether -Inf < x < Inf.
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// A NaN is not finite.
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func (x *Float) IsFinite() bool {
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return len(x.mant) != 0 || x.exp == 0
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}
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// IsInf reports whether x is a +Inf or -Inf.
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func (x *Float) IsInf() bool {
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return x.exp == infExp
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}
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// IsNaN reports whether x is a NaN.
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func (x *Float) IsNaN() bool {
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return x.exp == nanExp
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}
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// IsInt reports whether x is an integer.
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// ±Inf and NaN are not considered integers.
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func (x *Float) IsInt() bool {
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@ -303,25 +302,6 @@ func (x *Float) IsInt() bool {
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return x.prec <= uint32(x.exp) || x.MinPrec() <= uint(x.exp) // not enough bits for fractional mantissa
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}
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// IsInf reports whether x is an infinity, according to sign.
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// If sign > 0, IsInf reports whether x is positive infinity.
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// If sign < 0, IsInf reports whether x is negative infinity.
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// If sign == 0, IsInf reports whether x is either infinity.
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func (x *Float) IsInf(sign int) bool {
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if debugFloat {
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validate(x)
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}
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return x.exp == infExp && (sign == 0 || x.neg == (sign < 0))
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}
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// IsNaN reports whether x is a NaN.
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func (x *Float) IsNaN() bool {
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if debugFloat {
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validate(x)
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}
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return x.exp == nanExp
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}
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func (z *Float) setZero() {
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z.mant = z.mant[:0]
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z.exp = 0
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@ -715,20 +695,20 @@ func (z *Float) Set(x *Float) *Float {
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return z
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}
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// Copy sets z to x, with the same precision and rounding mode as x,
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// and returns z.
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// Copy sets z to x, with the same precision, rounding mode, and
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// accuracy as x, and returns z. x is not changed even if z and
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// x are the same.
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func (z *Float) Copy(x *Float) *Float {
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if debugFloat {
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validate(x)
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}
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// TODO(gri) what about z.acc? should it be always Exact?
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if z != x {
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z.acc = Exact
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z.neg = x.neg
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z.exp = x.exp
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z.mant = z.mant.set(x.mant)
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z.prec = x.prec
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z.mode = x.mode
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z.acc = x.acc
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z.neg = x.neg
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z.mant = z.mant.set(x.mant)
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z.exp = x.exp
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}
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return z
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}
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@ -858,7 +838,7 @@ func (x *Float) Int64() (int64, Accuracy) {
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// Float64 returns the closest float64 value of x
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// by rounding to nearest with 53 bits precision.
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// BUG(gri) doesn't handle exponent overflow
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// BUG(gri) Float.Float64 doesn't handle exponent overflow.
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func (x *Float) Float64() (float64, Accuracy) {
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if debugFloat {
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validate(x)
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@ -955,7 +935,6 @@ func (x *Float) Int(z *Int) (*Int, Accuracy) {
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z = new(Int)
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}
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z.neg = x.neg
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// TODO(gri) should have a shift that takes positive and negative shift counts
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switch {
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case exp > allBits:
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z.abs = z.abs.shl(x.mant, exp-allBits)
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@ -1232,8 +1211,7 @@ func (x *Float) ucmp(y *Float) int {
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return 0
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}
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// Handling of sign bit as defined by IEEE 754-2008,
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// section 6.3 (note that there are no NaN Floats):
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// Handling of sign bit as defined by IEEE 754-2008, section 6.3:
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//
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// When neither the inputs nor result are NaN, the sign of a product or
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// quotient is the exclusive OR of the operands’ signs; the sign of a sum,
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@ -1252,14 +1230,13 @@ func (x *Float) ucmp(y *Float) int {
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//
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// See also: http://play.golang.org/p/RtH3UCt5IH
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// Add sets z to the rounded sum x+y and returns z.
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// If z's precision is 0, it is changed to the larger
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// of x's or y's precision before the operation.
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// Rounding is performed according to z's precision
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// and rounding mode; and z's accuracy reports the
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// result error relative to the exact (not rounded)
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// Add sets z to the rounded sum x+y and returns z. If z's precision is 0,
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// it is changed to the larger of x's or y's precision before the operation.
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// Rounding is performed according to z's precision and rounding mode; and
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// z's accuracy reports the result error relative to the exact (not rounded)
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// result.
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// BUG(gri) If any of the operands is Inf, the result is NaN.
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// BUG(gri) Float.Add returns NaN if an operand is Inf.
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// BUG(gri) When rounding ToNegativeInf, the sign of Float values rounded to 0 is incorrect.
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func (z *Float) Add(x, y *Float) *Float {
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if debugFloat {
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validate(x)
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@ -1314,7 +1291,7 @@ func (z *Float) Add(x, y *Float) *Float {
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// Sub sets z to the rounded difference x-y and returns z.
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// Precision, rounding, and accuracy reporting are as for Add.
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// BUG(gri) If any of the operands is Inf, the result is NaN.
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// BUG(gri) Float.Sub returns NaN if an operand is Inf.
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func (z *Float) Sub(x, y *Float) *Float {
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if debugFloat {
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validate(x)
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@ -1369,7 +1346,7 @@ func (z *Float) Sub(x, y *Float) *Float {
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// Mul sets z to the rounded product x*y and returns z.
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// Precision, rounding, and accuracy reporting are as for Add.
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// BUG(gri) If any of the operands is Inf, the result is NaN.
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// BUG(gri) Float.Mul returns NaN if an operand is Inf.
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func (z *Float) Mul(x, y *Float) *Float {
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if debugFloat {
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validate(x)
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@ -1407,7 +1384,7 @@ func (z *Float) Mul(x, y *Float) *Float {
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// Quo sets z to the rounded quotient x/y and returns z.
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// Precision, rounding, and accuracy reporting are as for Add.
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// BUG(gri) If any of the operands is Inf, the result is NaN.
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// BUG(gri) Float.Quo returns NaN if an operand is Inf.
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func (z *Float) Quo(x, y *Float) *Float {
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if debugFloat {
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validate(x)
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@ -1454,8 +1431,7 @@ func (z *Float) Quo(x, y *Float) *Float {
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//
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// Infinities with matching sign are equal.
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// NaN values are never equal.
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// BUG(gri) comparing NaN's is not implemented
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// (should we use Accuracy here for results?)
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// BUG(gri) Float.Cmp does not implement comparing of NaNs.
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func (x *Float) Cmp(y *Float) int {
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if debugFloat {
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validate(x)
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@ -1498,7 +1474,6 @@ func umax32(x, y uint32) uint32 {
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// +1 if 0 < x < +Inf
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// +2 if x == +Inf
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//
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// TODO(gri) export (and remove IsInf)?
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func (x *Float) ord() int {
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m := 1 // common case
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if len(x.mant) == 0 {
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@ -78,7 +78,7 @@ func TestFloatZeroValue(t *testing.T) {
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z := make(test.z)
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test.op(z, make(test.x), make(test.y))
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got := 0
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if !z.IsInf(0) && !z.IsNaN() {
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if z.IsFinite() {
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got = int(z.int64())
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}
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if got != test.want {
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@ -288,6 +288,38 @@ func TestFloatSetMantExp(t *testing.T) {
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}
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}
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func TestFloatPredicates(t *testing.T) {
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for _, test := range []struct {
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x string
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neg, zero, finite, inf, nan bool
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}{
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{x: "-Inf", neg: true, inf: true},
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{x: "-1", neg: true, finite: true},
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{x: "-0", neg: true, zero: true, finite: true},
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{x: "0", zero: true, finite: true},
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{x: "1", finite: true},
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{x: "+Inf", inf: true},
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{x: "NaN", nan: true},
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} {
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x := makeFloat(test.x)
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if got := x.IsNeg(); got != test.neg {
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t.Errorf("(%s).IsNeg() = %v; want %v", test.x, got, test.neg)
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}
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if got := x.IsZero(); got != test.zero {
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t.Errorf("(%s).IsZero() = %v; want %v", test.x, got, test.zero)
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}
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if got := x.IsFinite(); got != test.finite {
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t.Errorf("(%s).IsFinite() = %v; want %v", test.x, got, test.finite)
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}
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if got := x.IsInf(); got != test.inf {
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t.Errorf("(%s).IsInf() = %v; want %v", test.x, got, test.inf)
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}
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if got := x.IsNaN(); got != test.nan {
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t.Errorf("(%s).IsNaN() = %v; want %v", test.x, got, test.nan)
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}
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}
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}
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func TestFloatIsInt(t *testing.T) {
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for _, test := range []string{
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"0 int",
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@ -314,14 +346,6 @@ func TestFloatIsInt(t *testing.T) {
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}
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}
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func TestFloatIsInf(t *testing.T) {
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// TODO(gri) implement this
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}
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func TestFloatIsNaN(t *testing.T) {
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// TODO(gri) implement this
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}
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func fromBinary(s string) int64 {
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x, err := strconv.ParseInt(s, 2, 64)
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if err != nil {
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@ -740,10 +764,6 @@ func TestFloatSetInf(t *testing.T) {
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}
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}
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func TestFloatSetNaN(t *testing.T) {
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// TODO(gri) implement
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}
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func TestFloatUint64(t *testing.T) {
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for _, test := range []struct {
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x string
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|
@ -63,7 +63,7 @@ func (z *Float) SetString(s string) (*Float, bool) {
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// be binary, if present (an "e" or "E" exponent indicator cannot be
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// distinguished from a mantissa digit).
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//
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// BUG(gri) This signature conflicts with Scan(s fmt.ScanState, ch rune) error.
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// BUG(gri) The Float.Scan signature conflicts with Scan(s fmt.ScanState, ch rune) error.
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func (z *Float) Scan(r io.ByteScanner, base int) (f *Float, b int, err error) {
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if z.prec == 0 {
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z.prec = 64
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@ -224,7 +224,7 @@ func ParseFloat(s string, base int, prec uint, mode RoundingMode) (f *Float, b i
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// number of digits necessary such that ParseFloat will return f exactly.
|
||||
// The prec value is ignored for the 'b' or 'p' format.
|
||||
//
|
||||
// BUG(gri) Currently, Format does not accept negative precisions.
|
||||
// BUG(gri) Float.Format does not accept negative precisions.
|
||||
func (x *Float) Format(format byte, prec int) string {
|
||||
const extra = 10 // TODO(gri) determine a good/better value here
|
||||
return string(x.Append(make([]byte, 0, prec+extra), format, prec))
|
||||
@ -236,7 +236,7 @@ func (x *Float) Append(buf []byte, format byte, prec int) []byte {
|
||||
// TODO(gri) factor out handling of sign?
|
||||
|
||||
// Inf
|
||||
if x.IsInf(0) {
|
||||
if x.IsInf() {
|
||||
var ch byte = '+'
|
||||
if x.neg {
|
||||
ch = '-'
|
||||
@ -261,7 +261,7 @@ func (x *Float) Append(buf []byte, format byte, prec int) []byte {
|
||||
return x.bigFtoa(buf, format, prec)
|
||||
}
|
||||
|
||||
// BUG(gri): Currently, String uses x.Format('g', 10) rather than x.Format('g', -1).
|
||||
// BUG(gri): Float.String uses x.Format('g', 10) rather than x.Format('g', -1).
|
||||
func (x *Float) String() string {
|
||||
return x.Format('g', 10)
|
||||
}
|
||||
|
@ -12,7 +12,7 @@ import (
|
||||
// TODO(gri) add more examples
|
||||
|
||||
func ExampleFloat_Add() {
|
||||
// Operating on numbers of different precision is easy.
|
||||
// Operating on numbers of different precision.
|
||||
var x, y, z big.Float
|
||||
x.SetInt64(1000) // x is automatically set to 64bit precision
|
||||
y.SetFloat64(2.718281828) // y is automatically set to 53bit precision
|
||||
@ -22,9 +22,9 @@ func ExampleFloat_Add() {
|
||||
fmt.Printf("y = %s (%s, prec = %d, acc = %s)\n", &y, y.Format('p', 0), y.Prec(), y.Acc())
|
||||
fmt.Printf("z = %s (%s, prec = %d, acc = %s)\n", &z, z.Format('p', 0), z.Prec(), z.Acc())
|
||||
// Output:
|
||||
// x = 1000 (0x.fap10, prec = 64, acc = exact)
|
||||
// y = 2.718281828 (0x.adf85458248cd8p2, prec = 53, acc = exact)
|
||||
// z = 1002.718282 (0x.faadf854p10, prec = 32, acc = below)
|
||||
// x = 1000 (0x.fap10, prec = 64, acc = Exact)
|
||||
// y = 2.718281828 (0x.adf85458248cd8p2, prec = 53, acc = Exact)
|
||||
// z = 1002.718282 (0x.faadf854p10, prec = 32, acc = Below)
|
||||
}
|
||||
|
||||
func Example_Shift() {
|
||||
|
16
src/math/big/roundingmode_string.go
Normal file
16
src/math/big/roundingmode_string.go
Normal file
@ -0,0 +1,16 @@
|
||||
// generated by stringer -type=RoundingMode; DO NOT EDIT
|
||||
|
||||
package big
|
||||
|
||||
import "fmt"
|
||||
|
||||
const _RoundingMode_name = "ToNearestEvenToNearestAwayToZeroAwayFromZeroToNegativeInfToPositiveInf"
|
||||
|
||||
var _RoundingMode_index = [...]uint8{0, 13, 26, 32, 44, 57, 70}
|
||||
|
||||
func (i RoundingMode) String() string {
|
||||
if i+1 >= RoundingMode(len(_RoundingMode_index)) {
|
||||
return fmt.Sprintf("RoundingMode(%d)", i)
|
||||
}
|
||||
return _RoundingMode_name[_RoundingMode_index[i]:_RoundingMode_index[i+1]]
|
||||
}
|
Loading…
Reference in New Issue
Block a user