Add a convert method that allows for writting Float64(::SIQuantity) o…

…r Int(::SIQuantity)

src/SIUnits.jl

@@ -297,10 +297,11 @@ module SIUnits
     # Forwarding methods that do not affect units
     import Base: conj
     conj(x::SIQuantity) = typeof(x)(conj(x.val))
-
+    # remove when they are fully deprecated in 0.5 as the convert bellow covers all cases. As constructers call convert as fallback
     float64(x::SIQuantity) = float64(x.val)
     float(x::SIQuantity) = float(x.val)
     int(x::SIQuantity) = int(x.val)
+    convert{T1<:@compat(Union{Integer, AbstractFloat}), T<:Number,m,kg,s,A,K,mol,cd,rad,sr}(::Type{T1},x::SIQuantity{T,m,kg,s,A,K,mol,cd,rad,sr}) = convert(T1, x.val)
 
     *(x::SIUnit,y::SIUnit) = tup2u(tup(x)+tup(y))()
     *{T}(x::SIUnit,y::SIQuantity{T}) = to_q(quantity(T,tup(y)+tup(x)),y.val)

test/runtests.jl

@@ -172,3 +172,11 @@ for func in (sin,cos,tan,cot,sec,csc)
     @test func(1.23rad) == func(1.23)
     @test_approx_eq func(1.23deg) func(as(1.23deg,rad))
 end
+
+if VERSION <= v"0.4.0"
+    var = 5*V
+    for f in [Float32, Float64, Int64, Int32, UInt32, BigFloat]
+        @test f(var) = f(var.val)
+    end
+
+end