Special functions erf

[rayomaz]

Nice toolbox! Suggesting an extension to be able to handle erf from SpecialFunctions.jl. After testing, bounds look good on my end ;)

[mykelk]

Awesome! Are you able to bring in my most recent commit to main so that we can rerun the CI to ensure everything passes?

[rayomaz]

Great! Made a commit to match your latest CI file version. I belief the workflow should pass

[chelseas]

I appreciate the PR but this needs a little cleanup. E.g., this isn't needed if the convexity is properly set in get_regions_unary:

    if d2f_zeros === nothing && convex === nothing
        if f_x_expr isa Expr && f_x_expr.head == :call && f_x_expr.args[1] == :erf
            if ub <= 0
                d2f_zeros = Float64[]; convex = true       # erf convex on (-∞,0]
            elseif lb >= 0
                d2f_zeros = Float64[]; convex = false      # erf concave on [0,∞)
            else
                d2f_zeros = [0.0]; convex = nothing        # mixed across 0
            end
        end
    end
    ```
    
    

[chelseas]

Also, why goes get_symbols have to support erf?

And why is this necessary?

   # robust resolution: try current scope, then SpecialFunctions
    fun = try
        eval(:($f))
    catch
        getfield(SpecialFunctions, f)
    end

If SpecialFunctions is loaded, eval should handle it.

And this appears to be unfinished?

   function find_bounds_for_function(func::Symbol, range)
    if func == :erf
        # Evaluate erf over interval range using interval arithmetic
        return erf(range)
    elseif func in special_func
        # existing logic
    else
        error("Unsupported function: $func")
    end
end

[mykelk]

Also it looks like a conflict needs to be resolved due to a previous PR that was merged. Thanks for the PR!