dual exponent (JuliaDiff#605)

* add exponent(::Dual)

* revert spacing

Author: ptiede

src/dual.jl

@@ -332,6 +332,8 @@ Base.fld(x::Dual, y::Dual) = fld(value(x), value(y))
 
 Base.cld(x::Dual, y::Dual) = cld(value(x), value(y))
 
+Base.exponent(x::Dual) = exponent(value(x))
+
 if VERSION ≥ v"1.4"
     Base.div(x::Dual, y::Dual, r::RoundingMode) = div(value(x), value(y), r)
 else

test/DualTest.jl

@@ -155,6 +155,10 @@ for N in (0,3), M in (0,4), V in (Int, Float32)
         @test fld(FDNUM, PRIMAL2) === fld(PRIMAL, PRIMAL2)
         @test fld(PRIMAL, FDNUM2) === fld(PRIMAL, PRIMAL2)
 
+        @test exponent(FDNUM) === exponent(PRIMAL)
+        @test exponent(FDNUM2) === exponent(PRIMAL2)
+        @test exponent(NESTED_FDNUM) === exponent(PRIMAL)
+
         @test cld(FDNUM, FDNUM2) === cld(PRIMAL, PRIMAL2)
         @test cld(FDNUM, PRIMAL2) === cld(PRIMAL, PRIMAL2)
         @test cld(PRIMAL, FDNUM2) === cld(PRIMAL, PRIMAL2)