SymbolicUtils Test

ruletest.jl

using ModelingToolkit
using SymbolicUtils

@syms w x y z

# Rule using exp
rexp=@rule exp(~~xs) => ~~xs
A=rexp(exp(10*sin(w)+exp(z))) # Returns 10*sin(w)+exp(z)

# Rule using Differential
rdiff=@rule Differential(x)(~~xs*Differential(x)(w)) => ~~xs
B=rdiff(Differential(x)(sin(x)*sin(y)*Differential(x)(w))) # I expect sin(x)*sin(y), but I get nothing.

updated_ruletest.jl

using ModelingToolkit
using SymbolicUtils
using SymbolicUtils.Rewriters

@syms w x y z

# Function to determine if the input is a Differential
isDiff = T -> T isa Differential

# The IBP rule for single PD.
getargDiff = @rule (~x::isDiff)((~~w)) => ((~~w))*(~x);

#Function to do the IBP on all terms
function IBP(T, testFunc)
    opsum=0;
    if(length(SymbolicUtils.arguments(T))==1)
        opsum=getargDiff(T).outer*getargDiff(T).inner(testFunc);
        return opsum[1];
    else
        for X=SymbolicUtils.arguments(T)
            op=getargDiff(X).outer*getargDiff(X).inner(testFunc);
            opsum+=op[1];
        end
        return opsum;
    end
end

# Define the LHS of the Poisson Equation
Dx=Differential(x);
Dy=Differential(y);
DxkDx=Dx((sin(x)+exp(y))*Dx(w));
DykDy=Dy(Dy(w));
DD=DxkDx + DykDy;
@show DD # The Poisson equation

# Do the IBP
term1=IBP(DD, z) # The weak form of the LHS
@show term1