Re: STL like algorithms for Lua

[steve donovan <steve.j.donovan@...>]

On Fri, Apr 2, 2010 at 5:13 AM, King, Mike <MKing@klmicrowave.com> wrote:
> I'm sure you are right.  I don't think it can get any worse.

Here is one approach of using an STL-like approach, but with run-time
polymorphism not compile-time, of course.

Take the copy algorithm

t = {}
copy(ipairs(t1),t)

copy(ipairs(t),back_inserter(ls))

The Lua equivalent of *p++ which is happening in std:copy would be t[k] = v, so

function back_inserter(ls)
  return setmetatable({},{
    __newindex = function(t,k,v)
        table.insert(ls,v)
  end
 } end

And so on for front_inserter, etc.

Combining two tables (the 'union') would be:
res = {}
copy(pairs(t1),res)
copy(pairs(t2),res)

This gets a bit simpler with a sequence concatenation operation pairs2():

copy(pairs2(t1,t2),res)

By default, all sequences are treated as key-value pair values, so

copy(enum(io.lines()),t)

where enum works like Python's enumerate.

Of course, the proxy trick for back_inserter can be extended to I/O streams:

copy(ipairs(t),writer(io.stdout,'\n'))

And so on for copy_if, filter, etc.  An actual implementation can be
provided if people are interested, although it can always be an
exercise for the student ;)

steve d.