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Fixes classify function to detect subnormal floating points (#12836)

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* Fix classify to test for subnormality.
* Minor fix.
* Modified to maintain existing API.
* Minor change.
* Removed 32-bit case since float is always 64-bit.
This commit is contained in:
KeepCoolWithCoolidge
2019-12-08 12:17:11 -07:00
committed by Andreas Rumpf
parent 5da27a891c
commit ae7b53ec51
1 changed files with 19 additions and 15 deletions
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34
lib/pure/math.nim
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@@ -103,21 +103,23 @@ when defined(Posix) and not defined(genode):
{.passl: "-lm".}
const
PI* = 3.1415926535897932384626433 ## The circle constant PI (Ludolph's number)
TAU* = 2.0 * PI ## The circle constant TAU (= 2 * PI)
E* = 2.71828182845904523536028747 ## Euler's number
PI* = 3.1415926535897932384626433 ## The circle constant PI (Ludolph's number)
TAU* = 2.0 * PI ## The circle constant TAU (= 2 * PI)
E* = 2.71828182845904523536028747 ## Euler's number
MaxFloat64Precision* = 16 ## Maximum number of meaningful digits
## after the decimal point for Nim's
## ``float64`` type.
MaxFloat32Precision* = 8 ## Maximum number of meaningful digits
## after the decimal point for Nim's
## ``float32`` type.
MaxFloatPrecision* = MaxFloat64Precision ## Maximum number of
## meaningful digits
## after the decimal point
## for Nim's ``float`` type.
RadPerDeg = PI / 180.0 ## Number of radians per degree
MaxFloat64Precision* = 16 ## Maximum number of meaningful digits
## after the decimal point for Nim's
## ``float64`` type.
MaxFloat32Precision* = 8 ## Maximum number of meaningful digits
## after the decimal point for Nim's
## ``float32`` type.
MaxFloatPrecision* = MaxFloat64Precision ## Maximum number of
## meaningful digits
## after the decimal point
## for Nim's ``float`` type.
MinFloatNormal* = 2.225073858507201e-308 ## Smallest normal number for Nim's
## ``float`` type. (= 2^-1022).
RadPerDeg = PI / 180.0 ## Number of radians per degree
type
FloatClass* = enum ## Describes the class a floating point value belongs to.
@@ -140,6 +142,7 @@ proc classify*(x: float): FloatClass =
doAssert classify(0.0) == fcZero
doAssert classify(0.3/0.0) == fcInf
doAssert classify(-0.3/0.0) == fcNegInf
doAssert classify(5.0e-324) == fcSubnormal
# JavaScript and most C compilers have no classify:
if x == 0.0:
@@ -151,8 +154,9 @@ proc classify*(x: float): FloatClass =
if x > 0.0: return fcInf
else: return fcNegInf
if x != x: return fcNan
if abs(x) < MinFloatNormal:
return fcSubnormal
return fcNormal
# XXX: fcSubnormal is not detected!
proc isPowerOfTwo*(x: int): bool {.noSideEffect.} =
## Returns ``true``, if ``x`` is a power of two, ``false`` otherwise.