Re: Separator in table concatenation

[Luis Carvalho <lexcarvalho@...>]

> It would be nice if table.concat behaved like string.gsub:
>    table.concat(tbl,sep)
> would allow `sep` to be not only a string, but also a table or
> function, indexed or called with the current list index.

If `sep` depends on the index then isn't it better to simply "merge" tbl and
a `sep` table and then concat the result?

Alternatively, you might want to have a slightly more general concat function
that pre-formats table entries:

table.gconcat = function (t, sep, format)
  local f = format ~= nil and {} or t
  if format ~= nil then
    assert(type(format) == "function", "function expected")
    for i, v in ipairs(t) do f[i] = format(v, i) end
  end
  return table.concat(f, sep)
end

> E.g.
>   tbl = {"A","B","C"}
>   enumerate = function(k)
>      return ", "..tostring(k+1)..": "
>   end
>   print("1: "..table.concat(tbl,enumerate))
> 1: A, 2: B, 3: C

format = function (fmt)
  return function (v, i) return fmt:format(i, v) end
end

tbl = {"A", "B", "C"}
print(table.gconcat(tbl, ", ", format"%d: %s"))


Cheers,
Luis

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-- 
Luis Carvalho (Kozure)
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