From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.5-pre1 (2020-06-20) on
	ip-172-31-74-118.ec2.internal
X-Spam-Level: 
X-Spam-Status: No, score=-1.9 required=3.0 tests=BAYES_00 autolearn=ham
	autolearn_force=no version=3.4.5-pre1
Path: eternal-september.org!reader02.eternal-september.org!news.gegeweb.eu!gegeweb.org!usenet-fr.net!proxad.net!feeder1-2.proxad.net!cleanfeed3-a.proxad.net!nnrp1-1.free.fr!not-for-mail
Newsgroups: comp.lang.ada
References: <c4cce4e8-8b69-4a0a-b628-921c1b845dcfn@googlegroups.com>
 <fc7db0da-59f3-4b50-be41-98b8f3eb8ca5n@googlegroups.com>
 <5126648c-215e-4d9e-bdd9-82fa5b510896n@googlegroups.com>
 <5ffa2a7b$0$19459$426a74cc@news.free.fr> <rteidn$1to4$1@gioia.aioe.org>
From: DrPi <314@drpi.fr>
Subject: Re: From_string(Arg : String) return Big_Integer
Date: Sun, 10 Jan 2021 16:48:23 +0100
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101
 Thunderbird/78.6.0
MIME-Version: 1.0
In-Reply-To: <rteidn$1to4$1@gioia.aioe.org>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Language: fr
Content-Transfer-Encoding: 8bit
Message-ID: <5ffb21c8$0$21590$426a74cc@news.free.fr>
Organization: Guest of ProXad - France
NNTP-Posting-Date: 10 Jan 2021 16:48:25 CET
NNTP-Posting-Host: 82.65.30.55
X-Trace: 1610293705 news-3.free.fr 21590 82.65.30.55:50605
X-Complaints-To: abuse@proxad.net
Xref: reader02.eternal-september.org comp.lang.ada:61088
List-Id: <comp.lang.ada>


>> A much simpler function for Integer :
>>
>>     function Int_From_String (Str : String) return Integer is
>>        Num : Integer := 0;
>>     begin
>>        for C of Str loop
> 
> for C in Str'Range loop
In this case, C is a universal integer, not a character...

> 
>>           Num := (Num * 10) + Integer'Value((1 => C));
> 
>     Num := Num * 10 + Character'Pos (C) - Character'Pos'('0');
... so you have to use :
Num := Num * 10 + Character'Pos (Str(C)) - Character'Pos'('0');

I prefer this construct but when I quickly tried it, it did'nt work. 
Surely a typo somewhere.

So either :

       for C of Str loop
          Num := (Num * 10) + Character'Pos (C) - Character'Pos ('0');
       end loop;

or :

       for Idx in Str'Range loop
          Num := (Num * 10) + Character'Pos (Str(Idx)) - Character'Pos 
('0');
       end loop;




> 
>> Notes :
>> - I don't have a 202x compiler, so I can't check if it works with big 
>> ints.
>> - It does not manage the sign (like the function you designed).
> 
> - It does not handle overflow;
It handles overflow.

> - It does not handle missing numbers in the input;
> - It does not handle malformed input;
> - It does not handle bases other than 10;
> - It does not handle blank characters at the ends.
Sure. A very simple implementation usable in a known and controlled context.
> 
> Functions mimicking S'Value (X) cover only half of cases. For the other 
> half you need to get the number from a part of the string, so you have 
> to recognize the end of the number and return the index or position 
> where it ends or another token begins.
>