Use values in iszero (#635)

* Use values in iszero

* Special case empty coeff vectors

* Check for zero coefficients first

* Fix typo

Author: jishnub

src/Fun.jl

@@ -773,7 +773,7 @@ isapprox(g::Number, f::Fun; kw...) = isapprox(g*ones(space(f)), f; kw...)
 isreal(f::Fun{<:RealSpace,<:Real}) = true
 isreal(f::Fun) = false
 
-iszero(f::Fun)    = all(iszero,f.coefficients)
+iszero(f::Fun)    = all(iszero, coefficients(f)) || all(iszero, values(f))
 
 # Deliberately not named isconst or isconstant to avoid conflicts with Base or DomainSets
 isconstantfun(f::Fun) = iszero(f - first(f))

test/SpacesTest.jl

@@ -208,6 +208,11 @@ using Test
             F = Fun{typeof(PointSpace(1:3)), Float32}
             @test ApproxFunBase.cfstype(F) == Float32
         end
+
+        @testset "isconstantfun" begin
+            f = Fun(PointSpace(1:4), ones(4))
+            @test ApproxFunBase.isconstantfun(f)
+        end
     end
 
     @testset "DiracSpace" begin