Tweak isinf code, now independent of hardware

Author: musm

base/float.jl

@@ -503,7 +503,7 @@ isfinite(x::Float16) = reinterpret(UInt16,x)&0x7c00 != 0x7c00
 isfinite(x::Real) = decompose(x)[3] != 0
 isfinite(x::Integer) = true
 
-isinf(x::Real) = !isnan(x) & !isfinite(x)
+isinf(x::Real) = (reinterpret(Unsigned, x) & ~sign_mask(T)) == exponent_mask(T)
 
 ## hashing small, built-in numeric types ##
 

base/math.jl

@@ -411,25 +411,25 @@ Return `(x,exp)` such that `x` has a magnitude in the interval ``[1/2, 1)`` or 0
 and `val` is equal to ``x \\times 2^{exp}``.
 """
 function frexp{T<:AbstractFloat}(x::T)
-    xu = reinterpret(Unsigned, x)
+    xu = reinterpret(Unsigned,x)
     xe = xu & exponent_mask(T)
-    xe == exponent_mask(T) && return x, 0 # NaN or Inf
     k = Int(xe >> significand_bits(T))
     if xe == 0 # x is subnormal
+        x == 0 && return x, 0
         xs = xu & sign_mask(T)
         xu $= xs
-        xu == 0 && return x, 0 # +-0
-        m = (leading_zeros(xu) - exponent_bits(T)) % UInt
+        m = leading_zeros(xu)-exponent_bits(T)
         xu <<= m
         xu $= xs
-        k = 1 - (m % Int)
+        k = 1-m
+    elseif xe == exponent_mask(T) # NaN or Inf
+        return x,0
     end
-    k -= (exponent_bias(T) - 1)
+    k -= (exponent_bias(T)-1)
     xu = (xu & ~exponent_mask(T)) | exponent_half(T)
-    return reinterpret(T, xu), k
+    reinterpret(T,xu), k
 end
 
-
 function frexp{T<:AbstractFloat}(A::Array{T})
     F = similar(A)
     E = Array{Int}(size(A))