support prevfloat(x, int) (JuliaLang#28019)

halleysfifthinc · Jul 11, 2018 · 93e8651 · 93e8651
1 parent 324b30d
commit 93e8651
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Showing 2 changed files with 14 additions and 3 deletions.
diff --git a/base/float.jl b/base/float.jl
@@ -591,7 +591,7 @@ uabs(x::BitSigned) = unsigned(abs(x))
 
 
 """
- nextfloat(x::AbstractFloat, n::Integer)
+ nextfloat(x::IEEEFloat, n::Integer)
 
 The result of `n` iterative applications of `nextfloat` to `x` if `n >= 0`, or `-n`
 applications of `prevfloat` if `n < 0`.
@@ -642,6 +642,14 @@ such `y` exists (e.g. if `x` is `Inf` or `NaN`), then return `x`.
 """
 nextfloat(x::AbstractFloat) = nextfloat(x,1)
 
+"""
+ prevfloat(x::AbstractFloat, n::Integer)
+
+The result of `n` iterative applications of `prevfloat` to `x` if `n >= 0`, or `-n`
+applications of `nextfloat` if `n < 0`.
+"""
+prevfloat(x::AbstractFloat, d::Integer) = nextfloat(x, -d)
+
 """
  prevfloat(x::AbstractFloat)
 

diff --git a/test/math.jl b/test/math.jl
@@ -56,8 +56,11 @@ end
  end
 
  for (a,b) in [(T(12.8),T(0.8)),
- (prevfloat(realmin(T)), nextfloat(one(T),-2)),
- (nextfloat(zero(T),3), T(0.75)),
+ (prevfloat(realmin(T)), prevfloat(one(T), 2)),
+ (prevfloat(realmin(T)), prevfloat(one(T), 2)),
+ (prevfloat(realmin(T)), nextfloat(one(T), -2)),
+ (nextfloat(zero(T), 3), T(0.75)),
+ (prevfloat(zero(T), -3), T(0.75)),
  (nextfloat(zero(T)), T(0.5))]
 
  n = Int(log2(a/b))