gitee.com/quant1x/num@v0.3.2/math32/bits.go (about)

     1  package math32
     2  
     3  const (
     4  	uvnan    = 0x7FE00000
     5  	uvinf    = 0x7F800000
     6  	uvneginf = 0xFF800000
     7  	mask     = 0xFF
     8  	shift    = 32 - 8 - 1
     9  	bias     = 127
    10  	signMask = 1 << 31
    11  	fracMask = 1<<shift - 1
    12  )
    13  
    14  // Inf returns positive infinity if sign >= 0, negative infinity if sign < 0.
    15  func Inf(sign int) float32 {
    16  	var v uint32
    17  	if sign >= 0 {
    18  		v = uvinf
    19  	} else {
    20  		v = uvneginf
    21  	}
    22  	return Float32frombits(v)
    23  }
    24  
    25  // NaN returns an IEEE 754 “not-a-number” value.
    26  func NaN() float32 { return Float32frombits(uvnan) }
    27  
    28  // IsNaN reports whether f is an IEEE 754 “not-a-number” value.
    29  func IsNaN(f float32) (is bool) {
    30  	// IEEE 754 says that only NaNs satisfy f != f.
    31  	// To avoid the floating-point hardware, could use:
    32  	// x := Float32bits(f)
    33  	// return uint32(x>>shift)&mask == mask && x != uvinf && x != uvneginf
    34  	return f != f
    35  }
    36  
    37  // IsInf reports whether f is an infinity, according to sign.
    38  // If sign > 0, IsInf reports whether f is positive infinity.
    39  // If sign < 0, IsInf reports whether f is negative infinity.
    40  // If sign == 0, IsInf reports whether f is either infinity.
    41  func IsInf(f float32, sign int) bool {
    42  	// Test for infinity by comparing against maximum float.
    43  	// To avoid the floating-point hardware, could use:
    44  	// x := Float32bits(f)
    45  	// return sign >= 0 && x == uvinf || sign <= 0 && x == uvneginf
    46  	return sign >= 0 && f > MaxFloat32 || sign <= 0 && f < -MaxFloat32
    47  }
    48  
    49  // normalize returns a normal number y and exponent exp
    50  // satisfying x == y × 2**exp. It assumes x is finite and non-zero.
    51  func normalize(x float32) (y float32, exp int) {
    52  	const SmallestNormal = 1.1754943508222875079687365e-38 // 2**-(127 - 1)
    53  	if Abs(x) < SmallestNormal {
    54  		return x * (1 << shift), -shift
    55  	}
    56  	return x, 0
    57  }