Merge pull request #62 from ggggggggg/pull-request/77313054

readable DimensionError message

NEWS.md

@@ -1,6 +1,7 @@
 - v0.1.5
   - Patch for Julia PR [#20889](https://github.com/JuliaLang/julia/pull/20889), which changes how lowering is done for exponentiation of integer literals.
   - Bug fix to enable registering Main as a module for `u_str` (fixes [#61](https://github.com/ajkeller34/Unitful.jl/issues/61)).
+  - Implement readable message for `DimensionError` [#62](https://github.com/ajkeller34/Unitful.jl/pull/62).
 - v0.1.4
   - Critical bug fix owing to `mod_fast` changes.
 - v0.1.3

src/Conversion.jl

@@ -29,7 +29,7 @@ function uconvert(a::Units, x::Number)
     if dimension(a) == NoDims
         Quantity(x * convfact(a, NoUnits), a)
     else
-        throw(DimensionError())
+        throw(DimensionError(a,x))
     end
 end
 
@@ -47,7 +47,7 @@ Find the conversion factor from unit `t` to unit `s`, e.g. `convfact(m,cm) = 0.0
     # Check if conversion is possible in principle
     sdim = dimension(s())
     tdim = dimension(t())
-    sdim != tdim && throw(DimensionError())
+    sdim != tdim && throw(DimensionError(s(),t()))
 
     # first convert to base SI units.
     # fact1 is what would need to be multiplied to get to base SI units
@@ -133,7 +133,7 @@ function convert{T,D,U}(::Type{Quantity{T,D,U}}, x::Number)
     if dimension(x) == D()
         Quantity(T(uconvert(U(),x).val), U())
     else
-        throw(DimensionError())
+        throw(DimensionError(U(),x))
     end
 end
 
@@ -179,7 +179,7 @@ function convert{T,U}(::Type{DimensionlessQuantity{T,U}}, x::Quantity)
     if dimension(x) == NoDims
         Quantity(T(x.val), U())
     else
-        throw(DimensionError())
+        throw(DimensionError(NoDims,x))
     end
 end
 

src/Promotion.jl

@@ -7,7 +7,7 @@
             if dimension(S())==dimension(T())
                 promote_type(S,T)
             else
-                throw(DimensionError())
+                throw(DimensionError(S(),T()))
             end
         end
     end
@@ -18,7 +18,7 @@
             if dimension(S())==dimension(T())
                 promote_type(S,T)
             else
-                throw(DimensionError())
+                throw(DimensionError(S(),T()))
             end
         end
     end
@@ -35,7 +35,7 @@
         ::Type{Quantity{T1,D1,U1}}, ::Type{Quantity{T2,D2,U2}})
         # figuring out numeric type can be subtle if D1 == D2 but U1 != U2.
         # in particular, consider adding 1m + 1cm... the numtype is not Int.
-        D1 != D2 && throw(DimensionError())
+        D1 != D2 && throw(DimensionError(U1(),U2()))
         return Bool
     end
     function promote_op{T1,D1,U1,T2,D2,U2}(op, x::Type{Quantity{T1,D1,U1}},
@@ -62,7 +62,7 @@
         ::Type{R}, ::Type{Quantity{S,D,U}})
         # figuring out numeric type can be subtle if D1 == D2 but U1 != U2.
         # in particular, consider adding 1m + 1cm... the numtype is not Int.
-        D != Dimensions{()} && throw(DimensionError())
+        D != Dimensions{()} && throw(DimensionError(NoDims,U()))
         return Bool
     end
     function promote_op{R<:Number,S,D,U}(op, ::Type{R}, ::Type{Quantity{S,D,U}})
@@ -86,7 +86,7 @@
         ::Type{Quantity{S,D,U}}, ::Type{R})
         # figuring out numeric type can be subtle if D1 == D2 but U1 != U2.
         # in particular, consider adding 1m + 1cm... the numtype is not Int.
-        D != Dimensions{()} && throw(DimensionError())
+        D != Dimensions{()} && throw(DimensionError(NoDims,U()))
         return Bool
     end
     function promote_op{R<:Number,S,D,U}(op, x::Type{Quantity{S,D,U}}, y::Type{R})

src/Unitful.jl

@@ -49,12 +49,21 @@ const NoDims = Dimensions{()}()
 
 """
 ```
-type DimensionError <: Exception end
+type DimensionError{T,S} <: Exception
+  x::T
+  y::S
+end
 ```
 
 Thrown when dimensions don't match in an operation that demands they do.
+Display `x` and `y` in error message.
 """
-type DimensionError <: Exception end
+type DimensionError{T,S} <: Exception
+    x::T
+    y::S
+end
+Base.showerror(io::IO, e::DimensionError) =
+    print(io,"DimensionError: $(e.x) and $(e.y) are not dimensionally compatible.");
 
 """
 ```
@@ -403,19 +412,19 @@ for op in [:+, :-]
         :($($op)(uconvert($result_units, x), uconvert($result_units, y)))
     end
 
-    @eval ($op)(::Quantity, ::Quantity) = throw(DimensionError())
+    @eval ($op)(x::Quantity, y::Quantity) = throw(DimensionError(x,y))
     @eval function ($op)(x::Quantity, y::Number)
         if isa(x, DimensionlessQuantity)
             ($op)(promote(x,y)...)
         else
-            throw(DimensionError())
+            throw(DimensionError(x,y))
         end
     end
     @eval function ($op)(x::Number, y::Quantity)
         if isa(y, DimensionlessQuantity)
             ($op)(promote(x,y)...)
         else
-            throw(DimensionError())
+            throw(DimensionError(x,y))
         end
     end
 
@@ -673,7 +682,7 @@ for (_x,_y) in [(:fma, :_fma), (:muladd, :_muladd)]
     # It seems like most of this is optimized out by the compiler, including the
     # apparent runtime check of dimensions, which does not appear in @code_llvm.
     @eval @inline function ($_y)(x,y,z)
-        dimension(x) * dimension(y) != dimension(z) && throw(DimensionError())
+        dimension(x) * dimension(y) != dimension(z) && throw(DimensionError(x*y,z))
         uI = unit(x)*unit(y)
         uF = promote_type(typeof(uI), typeof(unit(z)))()
         c = ($_x)(ustrip(x), ustrip(y), ustrip(uconvert(uI, z)))
@@ -722,14 +731,14 @@ end
 atan2(y::Quantity, x::Quantity) = atan2(promote(y,x)...)
 atan2{T,D,U}(y::Quantity{T,D,U}, x::Quantity{T,D,U}) = atan2(y.val,x.val)
 atan2{T,D1,U1,D2,U2}(y::Quantity{T,D1,U1}, x::Quantity{T,D2,U2}) =
-    throw(DimensionError())
+    throw(DimensionError(x,y))
 
 for (f, F) in [(:min, :<), (:max, :>)]
     @eval @generated function ($f)(x::Quantity, y::Quantity)
         xdim = x.parameters[2]()
         ydim = y.parameters[2]()
         if xdim != ydim
-            return :(throw(DimensionError()))
+            return :(throw(DimensionError(x,y)))
         end
 
         xunits = x.parameters[3].parameters[1]
@@ -768,7 +777,7 @@ flipsign(x::Quantity, y::Number) = Quantity(flipsign(x.val,y/unit(y)), unit(x))
 
 @inline isless{T,D,U}(x::Quantity{T,D,U}, y::Quantity{T,D,U}) = _isless(x,y)
 @inline _isless{T,D,U}(x::Quantity{T,D,U}, y::Quantity{T,D,U}) = isless(x.val, y.val)
-@inline _isless{T,D1,D2,U1,U2}(x::Quantity{T,D1,U1}, y::Quantity{T,D2,U2}) = throw(DimensionError())
+@inline _isless{T,D1,D2,U1,U2}(x::Quantity{T,D1,U1}, y::Quantity{T,D2,U2}) = throw(DimensionError(x,y))
 @inline _isless(x,y) = isless(x,y)
 
 isless(x::Quantity, y::Quantity) = _isless(promote(x,y)...)
@@ -777,7 +786,7 @@ isless(x::Number, y::Quantity) = _isless(promote(x,y)...)
 
 @inline <{T,D,U}(x::Quantity{T,D,U}, y::Quantity{T,D,U}) = _lt(x,y)
 @inline _lt{T,D,U}(x::Quantity{T,D,U}, y::Quantity{T,D,U}) = <(x.val,y.val)
-@inline _lt{T,D1,D2,U1,U2}(x::Quantity{T,D1,U1}, y::Quantity{T,D2,U2}) = throw(DimensionError())
+@inline _lt{T,D1,D2,U1,U2}(x::Quantity{T,D1,U1}, y::Quantity{T,D2,U2}) = throw(DimensionError(x,y))
 @inline _lt(x,y) = <(x,y)
 
 <(x::Quantity, y::Quantity) = _lt(promote(x,y)...)

src/range.jl

@@ -10,18 +10,18 @@
     linspace(Float64, ustrip(start), ustrip(stop), len, 1)*unit(T)
 
 function _linspace{T}(start::Quantity{T}, stop::Quantity{T}, len::Integer)
-    dimension(start) != dimension(stop) && throw(DimensionError())
+    dimension(start) != dimension(stop) && throw(DimensionError(start, stop))
     linspace(start, stop, len)
 end
 
 @compat function colon(start::Quantity{<:Real}, step, stop::Quantity{<:Real})
-    dimension(start) != dimension(stop) && throw(DimensionError())
+    dimension(start) != dimension(stop) && throw(DimensionError(start, stop))
     T = promote_type(typeof(start),typeof(stop))
     return colon(convert(T,start), step, convert(T,stop))
 end
 
 function colon(start::A, step::B, stop::A) where A<:Quantity{<:Real} where B<:Quantity{<:Real}
-    dimension(start) != dimension(step) && throw(DimensionError())
+    dimension(start) != dimension(step) && throw(DimensionError(start, step))
     colon(promote(start, step, stop)...)
 end
 

test/runtests.jl

@@ -839,6 +839,17 @@ end
     end
 end
 
+@testset "DimensionError message" begin
+  function errorstr(e)
+    b = IOBuffer()
+    Base.showerror(b,e)
+    String(b)
+  end
+  @test errorstr(DimensionError(1u"m",2)) == "DimensionError: 1 m and 2 are not dimensionally compatible."
+  @test errorstr(DimensionError(1u"m",NoDims)) == "DimensionError: 1 m and  are not dimensionally compatible."
+  @test errorstr(DimensionError(u"m",2)) == "DimensionError: m and 2 are not dimensionally compatible."
+end
+
 # Test that the @u_str macro will find units in other modules.
 module ShadowUnits
     using Unitful