Re: STL like algorithms for Lua

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

On Sun, Apr 4, 2010 at 2:00 PM, steve donovan <steve.j.donovan@gmail.com> wrote:
> Take the copy algorithm
>
> t = {}
> copy(ipairs(t1),t)

The problem, of course, is that functions like pairs & ipairs do not
return a single value. So it has to be backwards:

t = copy({},ipairs{10,20,30})
copy(inserter(t),ipairs{40,50})
copy(writer(io.stdout,' '),ipairs(t))

t = {}
copy(t,pairs{a=1,b=2})
copy(t,pairs{c=2,d=3})
--> t is {a=1,b=2,c=2,d=3}

Here's what the code looks like - very straightforward. Anyone wishing
to add the others can find them here:

http://www.cplusplus.com/reference/algorithm/

steve d.

-----------------
function copy (t,...)
    for k,v in ... do
        t[k] = v
    end
    return t
end

function copy_if (t,pred,...)
    for k,v in ... do
        if pred(v) then
            t[k] = v
        end
    end
    return t
end

local function _newindex_handler (handler)
    return setmetatable({},{
        __newindex = handler
    })
end

function inserter (ls)
    local append = table.insert
    return _newindex_handler(function(t,k,v)
        append(ls,v)
    end)
end

function writer (f,delim)
    return _newindex_handler(function(t,k,v)
        f:write(v)
        if delim then f:write(delim) end
    end)
end

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