Is there way to do math on type parameters for function defintions

General Usage
1

I would like to do something like this,

pt_to_line_dist(x::SVector{N-1},l::SVector{N}) where N <: UInt = print("hi")

Is it possible?

2

no

3

Math on type parameters is not possible. Also, your N <: UInt will not do what you expect. In this case, it’s likely that N isa Int (not isa UInt and definitely not <:UInt, which could only apply to a type rather than value). Note that isa is not something you can do with type parameters anyway.

You could implement this as

function pt_to_line_dist(x::SVector{N},l::SVector{M}) where {N,M}
    if N == M-1
        print("hi")
    else
        # do other stuff or throw an error
    end
end

Although in this case I wouldn’t bother with type parameters at all

function pt_to_line_dist(x::AbstractVector,l::AbstractVector)
    if length(x) == length(l)-1
        print("hi")
    else
        # do other stuff or throw an error
    end
end

When given SVectors for inputs, length will evaluate to a compile-time constant and the if/else block will get compiled away, leaving only the correct branch. When given non-static vectors, the code will still work but it will have to check at run-time which branch to use.

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