add more complete rational arithmetic

Author: kalmarek

src/rational.jl

@@ -20,9 +20,18 @@ function operate!(::typeof(one), x::Rational)
 end
 
 # +
-function promote_operation(::typeof(+), ::Type{Rational{S}}, ::Type{Rational{T}}) where {S,T}
+function promote_operation(::Union{typeof(+), typeof(-)}, ::Type{Rational{S}}, ::Type{Rational{T}}) where {S,T}
     return Rational{promote_sum_mul(S, T)}
 end
+
+function promote_operation(op::Union{typeof(+), typeof(-)}, ::Type{Rational{S}}, ::Type{I}) where {S,I<:Integer}
+    return promote_operation(op, Rational{S}, Rational{I})
+end
+
+function promote_operation(op::Union{typeof(+), typeof(-)}, ::Type{I}, ::Type{Rational{S}}) where {S,I<:Integer}
+    return promote_operation(op, Rational{S}, Rational{I})
+end
+
 function operate_to!(output::Rational, ::typeof(+), x::Rational, y::Rational)
     xd, yd = Base.divgcd(promote(x.den, y.den)...)
     # TODO Use `checked_mul` and `checked_add` like in Base
@@ -32,10 +41,26 @@ function operate_to!(output::Rational, ::typeof(+), x::Rational, y::Rational)
     return output
 end
 
-# -
-function promote_operation(::typeof(-), ::Type{Rational{S}}, ::Type{Rational{T}}) where {S,T}
-    return Rational{promote_sum_mul(S, T)}
+function operate_to!(output::Rational, ::typeof(+), x::Rational, y::Integer)
+    # TODO Use `checked_mul` and `checked_add` like in Base
+    operate_to!(output.num, *, x.den, y)
+    operate!(+, output.num, x.num)
+    operate_to!(output.den, *, x.den, oftype(x.den, 1))
+    return output
+end
+
+function operate_to!(output::Rational, ::typeof(+), y::Integer, x::Rational)
+    return operate_to!(output, +, x, y)
 end
+
+# unary -
+function operate_to!(output::Rational, ::typeof(-), x::Rational)
+    operate_to!(output.num, -, x.num)
+    operate_to!(output.den, copy, x.den)
+    return output
+end
+
+# binary -
 function operate_to!(output::Rational, ::typeof(-), x::Rational, y::Rational)
     xd, yd = Base.divgcd(promote(x.den, y.den)...)
     # TODO Use `checked_mul` and `checked_sub` like in Base
@@ -45,10 +70,35 @@ function operate_to!(output::Rational, ::typeof(-), x::Rational, y::Rational)
     return output
 end
 
+function operate_to!(output::Rational, ::typeof(-), x::Rational, y::Integer)
+    # TODO Use `checked_mul` and `checked_sub` like in Base
+    operate_to!(output.num, *, x.den, y)
+    operate!(-, output.num)
+    operate!(+, output.num, x.num)
+    operate_to!(output.den, copy, x.den)
+    return output
+end
+
+function operate_to!(output::Rational, ::typeof(-), y::Integer, x::Rational)
+    # TODO Use `checked_mul` and `checked_sub` like in Base
+    operate_to!(output, -, x, y)
+    operate_to!(output, -, output)
+    return output
+end
+
 # *
 function promote_operation(::typeof(*), ::Type{Rational{S}}, ::Type{Rational{T}}) where {S,T}
     return Rational{promote_operation(*, S, T)}
 end
+
+function promote_operation(::typeof(*), ::Type{Rational{S}}, ::Type{I}) where {S,I<:Integer}
+    return promote_operation(*, Rational{S}, Rational{I})
+end
+
+function promote_operation(::typeof(*), ::Type{I}, ::Type{Rational{S}}) where {S,I<:Integer}
+    return promote_operation(*, Rational{S}, Rational{I})
+end
+
 function operate_to!(output::Rational, ::typeof(*), x::Rational, y::Rational)
     xn, yd = Base.divgcd(promote(x.num, y.den)...)
     xd, yn = Base.divgcd(promote(x.den, y.num)...)
@@ -57,6 +107,48 @@ function operate_to!(output::Rational, ::typeof(*), x::Rational, y::Rational)
     return output
 end
 
+function operate_to!(output::Rational, ::typeof(*), x::Rational, y::Integer)
+    xn = x.num
+    xd, yn = Base.divgcd(promote(x.den, y)...)
+    operate_to!(output.num, *, xn, yn)
+    operate_to!(output.den, copy, x.den)
+    return output
+end
+
+function operate_to!(output::Rational, ::typeof(*), y::Integer, x::Rational)
+   return operate_to!(output, *, x, y)
+end
+
+# //
+function operate_to!(output::Rational, op::Union{typeof(/), typeof(//)}, x::Rational, y::Rational)
+    xn, yn = Base.divgcd(promote(x.num, y.num)...)
+    xd, yd = Base.divgcd(promote(x.den, y.den)...)
+    operate_to!(output.num, *, xn, yd)
+    operate_to!(output.den, *, xd, yn)
+    return output
+end
+
+function operate_to!(output::Rational, op::Union{typeof(/), typeof(//)}, x::Rational, y::Integer)
+    xn, yn = Base.divgcd(promote(x.num, y)...)
+    operate_to!(output.num, copy, xn)
+    operate_to!(output.den, *, x.den, yn)
+    return output
+end
+
+function operate_to!(output::Rational, op::Union{typeof(/), typeof(//)}, x::Integer, y::Rational)
+    xn, yd = Base.divgcd(promote(x, y.den)...)
+    operate_to!(output.num, *, xn, yd)
+    operate_to!(output.den, copy, y.num)
+    return output
+end
+
+function operate_to!(output::Rational, op::Union{typeof(/), typeof(//)}, x::Integer, y::Integer)
+    n, d = Base.divgcd(promote(x, y)...)
+    operate_to!(output.num, copy, n)
+    operate_to!(output.den, copy, d)
+    return output
+end
+
 # gcd
 function promote_operation(::Union{typeof(gcd),typeof(lcm)}, ::Type{Rational{S}}, ::Type{Rational{T}}) where {S,T}
     return Rational{promote_operation(gcd, S, T)}

test/rational.jl

@@ -0,0 +1,17 @@
+for op in (+, -, *, //)
+    for (a,b) in (
+            (2//3, 5), (2, 3//5), (2//3, 5//7),
+            (big(2)//3, 5), (big(2), 3//5), (big(2)//3, 5//7),
+        )
+        @test MA.operate_to!!(MA.copy_if_mutable(op(a,b)), op, a, b) == op(a, b)
+        @test MA.operate_to!!(MA.copy_if_mutable(op(b,a)), op, b, a) == op(b, a)
+    end
+end
+
+op = //
+for (a,b) in (
+    (2,3), (big(2), 3), (2, big(3))
+    )
+    @test MA.operate_to!!(MA.copy_if_mutable(op(a,b)), op, a, b) == op(a,b)
+    @test MA.operate_to!!(MA.copy_if_mutable(op(b,a)), op, b, a) == op(b,a)
+end

test/runtests.jl

@@ -14,6 +14,11 @@ end
 @testset "BigInt" begin
     include("big.jl")
 end
+
+@testset "Rational" begin
+    include("rational.jl")
+end
+
 @testset "Broadcast" begin
     include("broadcast.jl")
 end