Add hash method for quantities

Author: sostock

src/Unitful.jl

@@ -1,6 +1,6 @@
 module Unitful
 
-import Base: ==, <, <=, +, -, *, /, //, ^, isequal
+import Base: ==, <, <=, +, -, *, /, //, ^, isequal, hash
 import Base: show, convert
 import Base: abs, abs2, angle, big, float, fma, muladd, inv, sqrt, cbrt
 import Base: min, max, floor, ceil, real, imag, conj

src/quantities.jl

@@ -311,6 +311,11 @@ for cmp in [:(==), :isequal]
     @eval $cmp(x::Number, y::AbstractQuantity) = $cmp(y,x)
 end
 
+# For now, hashes of quantities that are equal but have different units are not equal
+function hash(x::AbstractQuantity, h::UInt)
+    hash(x.val, hash(FreeUnits(unit(x)), h))
+end
+
 _dimerr(f) = error("$f can only be well-defined for dimensionless ",
         "numbers. For dimensionful numbers, different input units yield physically ",
         "different results.")

test/runtests.jl

@@ -571,6 +571,16 @@ Unitful.uconvert(U::Unitful.Units, q::QQQ) = uconvert(U, Quantity(q.val, cm))
     end
 end
 
+@testset "Hashing" begin
+    @test hash(big(1.0)m) === hash(big(1.0)m)
+    @test hash(1.0m) === hash(1m)
+    @test hash(0.5m) === hash((1//2)m)
+    @test hash(2.0m) === hash(2.0ContextUnits(m, cm))
+    @test hash(3.0m) === hash(3.0FixedUnits(m))
+    @test_broken hash(0.5m) === hash(500mm)
+    @test_broken hash(1rad) === hash(1)
+end
+
 @testset "Unit string parsing" begin
     @test uparse("m") == m
     @test uparse("m,s") == (m,s)
@@ -2100,11 +2110,11 @@ end
         @testset ">> Level" begin
             @test big(3.0)dBm == big(3.0)dBm
             @test isequal(big(3.0)dBm, big(3.0)dBm)
-            @test_broken hash(big(3.0)dBm) == hash(big(3.0)dBm)
+            @test hash(big(3.0)dBm) == hash(big(3.0)dBm)
 
             @test @dB(3.0V/2.0V) == @dB(3V/V)
             @test isequal(@dB(3.0V/2.0V), @dB(3V/V))
-            @test_broken hash(@dB(3.0V/2.0V)) == hash(@dB(3V/V))
+            @test hash(@dB(3.0V/2.0V)) == hash(@dB(3V/V))
         end
 
         @testset ">> Gain" begin