Implement generic Int->UInt shift count conversion in one place only

base/gmp.jl

@@ -362,10 +362,6 @@ end
 
 >>>(x::BigInt, c::UInt) = x >> c
 
-<<(x::BigInt, c::Int) = c >= 0 ? x << unsigned(c) : x >> unsigned(-c)
->>(x::BigInt, c::Int) = c >= 0 ? x >> unsigned(c) : x << unsigned(-c)
->>>(x::BigInt, c::Int) = c >= 0 ? x >>> unsigned(c) : x << unsigned(-c)
-
 
 
 trailing_zeros(x::BigInt) = Int(ccall((:__gmpz_scan1, :libgmp), Culong, (Ptr{BigInt}, Culong), &x, 0))

base/operators.jl

@@ -126,7 +126,10 @@ end
 const .≤ = .<=
 const .≠ = .!=
 
-# core << >> and >>> takes Int as second arg
+# Core <<, >>, and >>> take either Int or UInt as second arg. Signed shift
+# counts can shift in either direction, and are translated here to unsigned
+# counts. Integer datatypes only need to implement the unsigned version.
+
 """
     <<(x, n)
 
@@ -146,12 +149,13 @@ julia> bits(Int8(12))
 ```
 See also [`>>`](:func:`>>`), [`>>>`](:func:`>>>`).
 """
-function <<(x,y::Integer)
-    typemin(Int) <= y <= typemax(Int) && return x << (y % Int)
-    (x >= 0 || y >= 0) && return zero(x)
+function <<(x, c::Integer)
+    typemin(Int) <= c <= typemax(Int) && return x << (c % Int)
+    (x >= 0 || c >= 0) && return zero(x)
     oftype(x, -1)
 end
-<<(x,y::Unsigned) = y <= typemax(UInt) ? x << (y % UInt) : zero(x)
+<<(x, c::Unsigned) = c <= typemax(UInt) ? x << (c % UInt) : zero(x)
+<<(x, c::Int) = c >= 0 ? x << unsigned(c) : x >> unsigned(-c)
 
 """
     >>(x, n)
@@ -183,12 +187,13 @@ julia> bits(Int8(-4))
 ```
 See also [`>>>`](:func:`>>>`), [`<<`](:func:`<<`).
 """
-function >>(x,y::Integer)
-    typemin(Int) <= y <= typemax(Int) && return x >> (y % Int)
-    (x >= 0 || y < 0) && return zero(x)
+function >>(x, c::Integer)
+    typemin(Int) <= c <= typemax(Int) && return x >> (c % Int)
+    (x >= 0 || c < 0) && return zero(x)
     oftype(x, -1)
 end
->>(x,y::Unsigned) = y <= typemax(UInt) ? x >> (y % UInt) : zero(x)
+>>(x, c::Unsigned) = c <= typemax(UInt) ? x >> (c % UInt) : zero(x)
+>>(x, c::Int) = c >= 0 ? x >> unsigned(c) : x << unsigned(-c)
 
 """
     >>>(x, n)
@@ -215,8 +220,9 @@ is equivalent to [`>>`](:func:`>>`).
 
 See also [`>>`](:func:`>>`), [`<<`](:func:`<<`).
 """
->>>(x,y::Integer) = typemin(Int) <= y <= typemax(Int) ? x >>> (y % Int) : zero(x)
->>>(x,y::Unsigned) = y <= typemax(UInt) ? x >>> (y % UInt) : zero(x)
+>>>(x, c::Integer) = typemin(Int) <= c <= typemax(Int) ? x >>> (c % Int) : zero(x)
+>>>(x ,c::Unsigned) = c <= typemax(UInt) ? x >>> (c % UInt) : zero(x)
+>>>(x, c::Int) = c >= 0 ? x >>> unsigned(c) : x << unsigned(-c)
 
 # fallback div, fld, and cld implementations
 # NOTE: C89 fmod() and x87 FPREM implicitly provide truncating float division,