avoid recursion in intpow (#105)

* avoid recursion in intpow

* Add explicit tests for intpow

Author: jishnub

src/Fun.jl

@@ -363,10 +363,13 @@ function intpow(f::Fun,k::Integer)
         ones(space(f))
     elseif k==1
         f
-    elseif k > 1
-        f*f^(k-1)
     else
-        1/f^(-k)
+        t = reduce(*, fill(f, abs(k)))
+        if k > 0
+            return t
+        else
+            return 1/t
+        end
     end
 end
 

test/SpacesTest.jl

@@ -36,6 +36,13 @@ import ApproxFunBase: PointSpace, HeavisideSpace, PiecewiseSegment, dimension, V
                 end
             end
         end
+        @testset "intpow" begin
+            @test ApproxFunBase.intpow(f, 0) == f^0 == Fun(space(f), ones(ncoefficients(f)))
+            for n in 1:3
+                @test ApproxFunBase.intpow(f, n) == f^n == reduce(*, fill(f, n))
+            end
+            @test ApproxFunBase.intpow(f,-2) == f^-2 == 1/(f*f)
+        end
     end
 
     @testset "Derivative operator for HeavisideSpace" begin