also export widemul (ref #6169)

widen methods for Rational and Complex

Author: JeffBezanson

NEWS.md

@@ -221,7 +221,8 @@ Library improvements
   * Ranges and arrays with the same elements are now unequal. This allows hashing
     and comparing ranges to be faster. ([#5778])
 
-  * New function `widen` for widening numeric types and values ([#6169])
+  * New function `widen` for widening numeric types and values, and `widemul`
+    for multiplying to a larger type ([#6169])
 
 Deprecated or removed
 ---------------------

base/complex.jl

@@ -26,6 +26,8 @@ promote_rule{T<:Real,S<:Real}(::Type{Complex{T}}, ::Type{S}) =
 promote_rule{T<:Real,S<:Real}(::Type{Complex{T}}, ::Type{Complex{S}}) =
     Complex{promote_type(T,S)}
 
+widen{T}(::Type{Complex{T}}) = Complex{widen(T)}
+
 real(z::Complex) = z.re
 imag(z::Complex) = z.im
 real(x::Real) = x

base/exports.jl

@@ -448,6 +448,7 @@ export
     uint64,
     uint8,
     unsigned,
+    widemul,
     zero,
 
 # specfun

base/gmp.jl

@@ -412,10 +412,8 @@ ndigits(x::BigInt, b::Integer=10) = x.size == 0 ? 1 : ndigits0z(x,b)
 
 isprime(x::BigInt, reps=25) = ccall((:__gmpz_probab_prime_p,:libgmp), Cint, (Ptr{BigInt}, Cint), &x, reps) > 0
 
-widemul(x::BigInt, y::BigInt)   = x*y
 widemul(x::Int128, y::Uint128)  = BigInt(x)*BigInt(y)
 widemul(x::Uint128, y::Int128)  = BigInt(x)*BigInt(y)
-widemul{T<:Integer}(x::T, y::T) = BigInt(x)*BigInt(y)
 
 prevpow2(x::BigInt) = x.size < 0 ? -prevpow2(-x) : (x <= 2 ? x : one(BigInt) << (ndigits(x, 2)-1))
 nextpow2(x::BigInt) = x.size < 0 ? -nextpow2(-x) : (x <= 2 ? x : one(BigInt) << ndigits(x-1, 2))

base/int.jl

@@ -486,14 +486,6 @@ end
 
 ## wide multiplication, Int128 multiply and divide ##
 
-widemul(x::Union(Int8,Uint8,Int16), y::Union(Int8,Uint8,Int16)) = int32(x)*int32(y)
-widemul(x::Uint16, y::Uint16) = uint32(x)*uint32(y)
-
-widemul(x::Int32, y::Int32) = int64(x)*int64(y)
-widemul(x::Uint32, y::Uint32) = uint64(x)*uint64(y)
-
-widemul(x::Integer, y::Integer) = widemul(promote(x,y)...)
-
 if WORD_SIZE==32
     function widemul(u::Int64, v::Int64)
         local u0::Uint64, v0::Uint64, w0::Uint64
@@ -564,9 +556,6 @@ if WORD_SIZE==32
     >>>(x::Int128,  y::Int32) = y == 0 ? x : box(Int128,lshr_int(unbox(Int128,x),unbox(Int32,y)))
     >>>(x::Uint128, y::Int32) = y == 0 ? x : box(Uint128,lshr_int(unbox(Uint128,x),unbox(Int32,y)))
 else
-    widemul(u::Int64, v::Int64) = int128(u)*int128(v)
-    widemul(u::Uint64, v::Uint64) = uint128(u)*uint128(v)
-
     *(x::Int128,  y::Int128)  = box(Int128,mul_int(unbox(Int128,x),unbox(Int128,y)))
     *(x::Uint128, y::Uint128) = box(Uint128,mul_int(unbox(Uint128,x),unbox(Uint128,y)))
 

base/number.jl

@@ -30,6 +30,8 @@ ctranspose(x::Number) = conj(x)
 inv(x::Number) = one(x)/x
 angle(z::Real) = atan2(zero(z), z)
 
+widemul(x::Number, y::Number) = widen(x)*widen(y)
+
 start(x::Number) = false
 next(x::Number, state) = (x, true)
 done(x::Number, state) = state

base/rational.jl

@@ -57,6 +57,8 @@ promote_rule{T<:Integer,S<:Integer}(::Type{Rational{T}}, ::Type{S}) = Rational{p
 promote_rule{T<:Integer,S<:Integer}(::Type{Rational{T}}, ::Type{Rational{S}}) = Rational{promote_type(T,S)}
 promote_rule{T<:Integer,S<:FloatingPoint}(::Type{Rational{T}}, ::Type{S}) = promote_type(T,S)
 
+widen{T}(::Type{Rational{T}}) = Rational{widen(T)}
+
 function rationalize{T<:Integer}(::Type{T}, x::FloatingPoint; tol::Real=eps(x))
     if isnan(x);       return zero(T)//zero(T); end
     if x < typemin(T); return -one(T)//zero(T); end

doc/stdlib/base.rst

@@ -3008,6 +3008,10 @@ Mathematical Functions
 
    Compute the number of digits in number ``n`` written in base ``b``.
 
+.. function:: widemul(x, y)
+
+   Multiply ``x`` and ``y``, giving the result as a larger type.
+
 Data Formats
 ------------
 

test/numbers.jl

@@ -1772,3 +1772,5 @@ end
 ## Note: this should change to e.g. Float128 at some point
 @test widen(Float64) === BigFloat
 @test widen(BigInt) === BigInt
+
+@test widemul(typemax(Int64),typemax(Int64)) == 85070591730234615847396907784232501249