cannot add Piecewise functions if intervals are not the same

[goretkin]

julia> s = Fun(sin, [0., 7.]);

julia> c = Fun(cos, [0., 7.]);

julia> as = abs(s);

julia> ac = abs(c);

julia> ac+as;
ERROR: assertion failed: domainscompatible(a,b)
 in conversion_rule at /Users/goretkin/.julia/v0.3/ApproxFun/src/Spaces/Ultraspherical/UltrasphericalOperators.jl:273
 in maxspace at /Users/goretkin/.julia/v0.3/ApproxFun/src/Fun/FunctionSpace.jl:109
 in maxspace at /Users/goretkin/.julia/v0.3/ApproxFun/src/Spaces/Modifier/VectorSpace.jl:149
 in + at /Users/goretkin/.julia/v0.3/ApproxFun/src/Fun/Fun.jl:119

I spent a couple of hours trying to figure out how I should implement this but I don't know enough about ApproxFun. I put what I started in a gist https://gist.github.com/goretkin/5d4fb776b9ef09f4bd1f

I think the point here is to add ac + as without recomputing the coefficients, though one stopgap could be to override the addition method on Fun{PiecewiseSpace} directly and compute Fun( (x)-> ac[x] + as[x], unique(merge_sorted(breaks(ac.space), breaks(as.space))))

[dlfivefifty]

Ah good point, since the intervals are different.  I think I just need to override maxspace to say we can convert to piecewise with all pieces…

PiecewiseSpace is far from well-developed

On 24 Nov 2014, at 3:28 pm, Gustavo Goretkin notifications@github.com wrote:

julia> s = Fun(sin, [0., 7.]);

julia> c = Fun(cos, [0., 7.]);

julia> as = abs(s);

julia> ac = abs(c);

julia> ac+as;
ERROR: assertion failed: domainscompatible(a,b)
in conversion_rule at /Users/goretkin/.julia/v0.3/ApproxFun/src/Spaces/Ultraspherical/UltrasphericalOperators.jl:273
in maxspace at /Users/goretkin/.julia/v0.3/ApproxFun/src/Fun/FunctionSpace.jl:109
in maxspace at /Users/goretkin/.julia/v0.3/ApproxFun/src/Spaces/Modifier/VectorSpace.jl:149
in + at /Users/goretkin/.julia/v0.3/ApproxFun/src/Fun/Fun.jl:119
I spent a couple of hours trying to figure out how I should implement this but I don't know enough about ApproxFun. I put what I started in a gist https://gist.github.com/goretkin/5d4fb776b9ef09f4bd1f https://gist.github.com/goretkin/5d4fb776b9ef09f4bd1f
I think the point here is to add ac + as without recomputing the coefficients, though one stopgap could be to override the addition method on Fun{PiecewiseSpace} directly and compute Fun( (x)-> ac[x] + as[x], unique(merge_sorted(breaks(ac.space), breaks(as.space))))

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[dlfivefifty]

OK, this should work now for PiecewiseSpace{ChebyshevSpace}. I override union to determine a space that contains two other spaces.