What is the best way to generate a function based on the other function definition?

General Usage
1

Let’s say I have a function

function compute(x::Vector, y::Vector)
     return (x' * y) / sum(y)
end

Both x and y are vector with 0 or 1 values on each cell.

Based on this definition, I want to automatically generate a function, where for the variable in the denominator (y), I created a matrix Y, the rest variables remain to be vectors. The generated function should be something like:

function compute_generated(x::Vector, Y::Matrix)
    n = size(Y, 1)
    result = 0
    for i = 1:n 
         result += x' * Y[:,i] / i
    end
    return result
end

What is the best way to perform this task?
I took a look at the Julia manual about macro and @generated function, but I am still confused about if the concept can be applied to the task.

Regards

2

I don’t understand how the two functions are related — in the first one the denominator is sum(y), in the kernel of the second one, i.

Generally, if you want to reduce a collection using a bivariate kernel function, look at mapreduce & friends. Generating a function from the source code of another functions is almost surely the wrong approach for what you are trying to do.

1 Like
3

I suspect this can be done with a macro, since the macro could look at the function you defined, break it apart and create a “different” function.

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4

I don’t know if this is what you are after but take a look at the mapslices function to apply a function to slices through a matrix.

5

I have some rules that translate one function to another. For examples:

  • only sum(x) and/or sum(y), and other linear manipulation on those are allowed in the denominator.
  • If sum(x) appears on the denominator, I need to to write a generated function that accept a matrix X. If it doesn’t appear, then the function should accept a vector x.

The goal is to create a library that make this process automatic, i.e. given someone write the original code, the library should automatically generate the transformed function.

6

Yea. it looks like macros is the right way to do this.

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