Improve inference in Fun * Operator (#112)

* improve bandwidth inference

* Add tests

* return type assertion in isafunctional

Author: jishnub

Project.toml

@@ -1,6 +1,6 @@
 name = "ApproxFunBase"
 uuid = "fbd15aa5-315a-5a7d-a8a4-24992e37be05"
-version = "0.5.10"
+version = "0.5.11"
 
 [deps]
 AbstractFFTs = "621f4979-c628-5d54-868e-fcf4e3e8185c"

src/Operators/Operator.jl

@@ -36,7 +36,7 @@ domain(A::Operator) = domain(domainspace(A))
 
 isconstspace(_) = false
 ## Functionals
-isafunctional(A::Operator) = size(A,1)==1 && isconstspace(rangespace(A))
+isafunctional(A::Operator)::Bool = size(A,1)==1 && isconstspace(rangespace(A))
 
 
 isonesvec(A) = A isa AbstractFill && getindex_value(A) == 1

src/Operators/general/algebra.jl

@@ -240,8 +240,13 @@ struct TimesOperator{T,BI} <: Operator{T}
     end
 end
 
-bandwidthssum(P, k) = bandwidthssum(P)[k]
+bandwidthssum(P, k::Integer) = bandwidthssum(P)[k]
 bandwidthssum(P) = mapreduce(bandwidths, (t1, t2) -> t1 .+ t2, P, init = (0,0))
+_bandwidthssum(A::Operator, B::Operator) = __bandwidthssum(bandwidths(A), bandwidths(B))
+__bandwidthssum(A::NTuple{2,InfiniteCardinal{0}}, B::NTuple{2,InfiniteCardinal{0}}) = A
+__bandwidthssum(A::NTuple{2,InfiniteCardinal{0}}, B) = A
+__bandwidthssum(A, B::NTuple{2,InfiniteCardinal{0}}) = B
+__bandwidthssum(A, B) = reduce((t1, t2) -> t1 .+ t2, (A, B), init = (0,0))
 
 TimesOperator(ops::Vector{Operator{T}},bi::Tuple{N1,N2}) where {T,N1,N2} =
     TimesOperator{T,typeof(bi)}(ops,bi)
@@ -251,13 +256,13 @@ TimesOperator(ops::Vector{OT}) where {OT<:Operator} =
     TimesOperator(convert(Vector{Operator{eltype(OT)}},ops),bandwidthssum(ops))
 
 TimesOperator(A::TimesOperator,B::TimesOperator) =
-    TimesOperator(Operator{promote_type(eltype(A),eltype(B))}[A.ops; B.ops])
+    TimesOperator(Operator{promote_type(eltype(A),eltype(B))}[A.ops; B.ops], _bandwidthssum(A, B))
 TimesOperator(A::TimesOperator,B::Operator) =
-    TimesOperator(Operator{promote_type(eltype(A),eltype(B))}[A.ops; B])
+    TimesOperator(Operator{promote_type(eltype(A),eltype(B))}[A.ops; B], _bandwidthssum(A, B))
 TimesOperator(A::Operator,B::TimesOperator) =
-    TimesOperator(Operator{promote_type(eltype(A),eltype(B))}[A; B.ops])
+    TimesOperator(Operator{promote_type(eltype(A),eltype(B))}[A; B.ops], _bandwidthssum(A, B))
 TimesOperator(A::Operator,B::Operator) =
-    TimesOperator(Operator{promote_type(eltype(A),eltype(B))}[A,B])
+    TimesOperator(Operator{promote_type(eltype(A),eltype(B))}[A,B], _bandwidthssum(A, B))
 
 
 ==(A::TimesOperator,B::TimesOperator)=A.ops==B.ops

test/SpacesTest.jl

@@ -27,6 +27,13 @@ import ApproxFunBase: PointSpace, HeavisideSpace, PiecewiseSegment, dimension, V
             @test (@inferred oftype(f, fany)) isa typeof(f)
         end
 
+        A = @inferred f * Multiplication(f)
+        @test A * f == f^3
+
+        @testset "inafunctional inference" begin
+            @test @inferred !ApproxFunBase.isafunctional(Multiplication(f))
+        end
+
         @testset "real/complex coefficients" begin
             c = [1:4;]
             for c2 in Any[c, c*im]