stdio performance in tango, stdlib, and perl

[Andrei Alexandrescu (See Website For Email)]

Vladimir Panteleev wrote:
> On Thu, 22 Mar 2007 01:40:15 +0200, Andrei Alexandrescu (See Website For Email) <SeeWebsiteForEmail at erdani.org> wrote:
> 
>> Essentially it's about information. The naive loop:
>>
>> while (readln(line)) {
>>    write(line);
>> }
>>
>> is guaranteed 100% to produce an accurate copy of its input. The version
>> that chops lines looks like:
>>
>> while (readln(line)) {
>>    writeln(line);
>> }
> 
> I'd just like to say that the chosen naming convention seems a bit unintuitive to me out of the following reasons:
> 
> 1) it seems odd that what you read with readln(), you need to write with write() and not writeln().

"Read a line. Write what you've read. Rinse. Lather. Repeat."

> 2) Pascal/Delphi/etc. have the ReadLn and WriteLn functions, but Pascal's ReadLn doesn't preserve line endings.

That's a mistake, simple as that. Pascal has made many other similar 
mistakes, see http://www.lysator.liu.se/c/bwk-on-pascal.html.

> 3) in my personal experience (of a number of smaller and larger console applications), it's much more often that I need to work with the contents of lines (without line endings), rather than with. If you need to copy data while preserving line endings, I would recommend using binary buffers for files - and I've no idea why would you use standard input/output for binary data anyway.

I understand that. But again, getting rid of information when you have 
it is a much better proposition than regaining information when you 
irremediably lost.

Think that a file is produced by a utility or transmission that sends 
messages separated by a single-char or multi-char separator. If your 
reading primitive omits the separator, you don't know whether the last 
line is a fragment of a broken transmission or a valid line.

"Just call chomp."

> 4) it's much easier to add a line ending than to remove it.

It's been already said: it's cheaper to remove it in all circumstances.

> Based on the above reasons, I would like to suggest to let readln() chop line endings, and perhaps have another function (getline?) which keeps them.

For more balkanization, cognitive load, and confusion?

"Just call chomp."


Andrei