Re: Addition of map() and filter().

[TNHarris <telliamed@...>]

On Mon, 12 Oct 2009 23:16:12 +0200
André Ericsson <eandre@gmail.com> wrote:

> local LOCAL_ToStringAllTemp = {};
> function tostringall(...)
> -- etc...

That's rather ugly.

I've learned that recursion isn't a dirty word in Lua, so it's not at
all difficult to write a 'map' function

    function map(f,...)
      if select('#',...) == 0 then return end
      return f((...)),map(f,select(2,...))
    end

Which could be optimized to use local variables only. However, that does
demonstrate one thing about Lua that I didn't expect. This...

    return something, F()

... isn't a tail-call. I thought it would be, but the comma operator is
enough to prevent the optimization. I think it would be a worthwhile
change to the VM to allow a tail-call in this case.

A function that I think is better done in C than Lua is a
complement to 'select', which could be called 'shift'.
shift(n,...) returns the values that select(n+1,...) skips over.

-- tom
telliamed@whoopdedo.org