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Re: Challenges of adding octal and hexadecimal escape sequences in strin
From: |
Jose E. Marchesi |
Subject: |
Re: Challenges of adding octal and hexadecimal escape sequences in strings |
Date: |
Sat, 31 Oct 2020 13:44:30 +0100 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/28.0.50 (gnu/linux) |
>> On Fri, Oct 30, 2020 at 05:51:44PM +0100, Jose E. Marchesi wrote:
>>>
>>> I don't think that is the desired behavior. If we define Poke strings
>>> as NULL-terminated, it is obvious they are not to contain any NULL
>>> byte. Now, we can achieve that by two ways:
>>>
>>> a) By doing what we do now, i.e to ignore any part of the string after a
>>> NULL character, in case one is inserted, or
>>>
>>> b) To emit an error whenever a 0 byte is attempted to be stored in a
>>> string value.
>>>
>>> Supposing we wanted to switch to b), at the moment the only ways to
>>> create a string value in Poke are:
>>>
>>> b1) Using a string literal, and
>>> b2) using a cast from uint<8> to string
>>>
>>> The first case is easy to implement: just emit a compile-time error if a
>>> string literal contains a null character.
>>>
>>> For the second case we have two choices: either to raise an exception
>>> when `8UB as string' is executed, or to keep the current behavior of
>>> generating an empty string "", but the latter would be an exception to
>>> the rule.
>>>
>>> That's why I prefer a) to b): it is more orthogonal, and can be
>>> explained by a single rule without needing any exceptions to the rule.
>>> Also, it comes handy to shorten strings :D
>>
>> What about a third way:
>>
>> c) Keep Poke strings as NULL-terminated. Treat using of NULL character in
>> string
>> literals as compilation error.
>>
>> The user cannot access data beyond the first NULL character, and having bytes
>> beyond that character doesn't make any sense.
>
> Isn't that a subset of b) above?
I would like to add, that I don't find the current situation (i.e. a))
confusing at all.
On the opposite, it can't be simpler: regardless of how you construct a
string (be it using a literal with escape sequences, or mapping it on an
IO space) the resulting string spans until the first NULL character
found.