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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: |
Fri, 30 Oct 2020 17:51:44 +0100 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/28.0.50 (gnu/linux) |
Hi Mohammad!
> I've added support for octal and hexadecimal escape sequences in strings.
> But there's a problem with Poke strings: they are null-terminated.
>
> Please consider the following example:
>
> ```poke
> defvar s = "a\0b";
>
> assert (s'length == 1);
> assert (s'size == 2#B);
> assert (s == "a");
> ```
>
> This behavior is IMHO annoying and counter-intuitive.
>
> The desired behavior (IMHO):
>
> ```poke
> defvar s = "a\0b";
>
> assert (s'length == 3);
> assert (s'size == 4#B);
> assert (s == "a\0b");
> assert (s + "cde" == "a\0bcde");
> ```
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