"strings are delimited by double quote character", where there's a character variable

"strings are delimited by double quote character", where there's a character variable

[Mehdi Saada]

I got a a Character variable gnat says it is a String, while functions taking it as parameter take only Characters. Mentions of the variable in the procedure: 
C: Character := ''; -- strings are delimited by double quote character
while C /= '' loop 
        Get(C); PUSH(C); 
end loop; 
while (C /= '') loop -- same here        
        Get(C); 
        PUSH(C); 
end loop;

Re: "strings are delimited by double quote character", where there's a character variable

[A. Cervetti]

A Character literal cannot be empty, i.e. it can be 'A'. ' ', but not ''.
So the compiler assumes you are trying to define an empty string ("") and warns you accordingly.

A.

Re: "strings are delimited by double quote character", where there's a character variable

[AdaMagica]

C: Character := ' ';  -- a space character
S: String := " ";  -- a string holding one space character
empty: String := "";  -- a string holding nothing

S(1) = C
S = C  is illegal - different types left and right

I'm not sure I understand your problem. Hope this helps.

Re: "strings are delimited by double quote character", where there's a character variable

[Jeffrey R. Carter]

On 12/01/2017 04:08 PM, Mehdi Saada wrote:
> C: Character := ''; -- strings are delimited by double quote character

'' is not a Character. It's not any legal Ada construct. The only place '' can 
occur in Ada is in a comment or a string literal.

Apparently the most common reason for '' that the GNAT error-message writers 
have seen is as a typo for "", hence the error message, which would be 
meaningful in such a case. Not very useful for someone who doesn't understand 
what a Character is.

-- 
Jeff Carter
"We call your door-opening request a silly thing."
Monty Python & the Holy Grail
17

Re: "strings are delimited by double quote character", where there's a character variable

[Dennis Lee Bieber]

	Is there a question somewhere in this?

On Fri, 1 Dec 2017 07:08:39 -0800 (PST), Mehdi Saada <00120260a@gmail.com>
declaimed the following:

>I got a a Character variable gnat says it is a String, while functions taking it as parameter take only Characters. Mentions of the variable in the procedure: 
>C: Character := ''; -- strings are delimited by double quote character
>while C /= '' loop 
>        Get(C); PUSH(C); 
>end loop; 
>while (C /= '') loop -- same here        
>        Get(C); 
>        PUSH(C); 
>end loop;


	I see nothing wrong with the above. There are NO " characters in the
example. There are pairs of ' characters, which are used to delimit
CHARACTER -- which would be obvious by just stepping the cursor through
them.

	An empty string would be...		:= "";
-- 
	Wulfraed                 Dennis Lee Bieber         AF6VN
    wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/

Re: "strings are delimited by double quote character", where there's a character variable

[Dennis Lee Bieber]

On Fri, 01 Dec 2017 12:23:28 -0500, Dennis Lee Bieber
<wlfraed@ix.netcom.com> declaimed the following:

>	I see nothing wrong with the above. There are NO " characters in the
>example. There are pairs of ' characters, which are used to delimit
>CHARACTER -- which would be obvious by just stepping the cursor through
>them.
>
>	An empty string would be...		:= "";

	And a small mea culpa -- I've not had to use character, so overlooked
that empty character is invalid.
-- 
	Wulfraed                 Dennis Lee Bieber         AF6VN
    wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/

Re: "strings are delimited by double quote character", where there's a character variable

[Mehdi Saada]

Well, I do understand what a character is (a certain enumeration litteral), but I did nonetheless mixed up with the idea of a null string or size 0. I'll initialise character variables with Ada.Latin_1.Nul then. Thanks.

Re: "strings are delimited by double quote character", where there's a character variable

[Shark8]

On Friday, December 1, 2017 at 8:08:41 AM UTC-7, Mehdi Saada wrote:
> I got a a Character variable gnat says it is a String, while functions taking it as parameter take only Characters. Mentions of the variable in the procedure: 
> C: Character := ''; -- strings are delimited by double quote character
> while C /= '' loop 
>         Get(C); PUSH(C); 
> end loop; 
> while (C /= '') loop -- same here        
>         Get(C); 
>         PUSH(C); 
> end loop;

The character you are using is referred to in Ada as "Apostrophe" (See Package Ada.Characters.Latin_1) the character referred to as a double-quote character is "Quotation". -- Respectively, these are Character'(''') and Character'('"').

String and Character are two separate types, though related, and are therefore not interchangeable. / A String is an array of Character, and thus can be specified via aggregate as ('H', 'e', 'l', 'l', 'o')... this would be rather tedious and so there exists a bit of syntactic sugar to specify a String: these are the Quotation delimiters and result in the previous value also being representable as "Hello".

Re: "strings are delimited by double quote character", where there's a character variable

[Keith Thompson]

Shark8 <onewingedshark@gmail.com> writes:
> On Friday, December 1, 2017 at 8:08:41 AM UTC-7, Mehdi Saada wrote:
>> I got a a Character variable gnat says it is a String, while
>> functions taking it as parameter take only Characters. Mentions of
>> the variable in the procedure:
>> C: Character := ''; -- strings are delimited by double quote character
>> while C /= '' loop 
>>         Get(C); PUSH(C); 
>> end loop; 
>> while (C /= '') loop -- same here        
>>         Get(C); 
>>         PUSH(C); 
>> end loop;
>
> The character you are using is referred to in Ada as "Apostrophe" (See
> Package Ada.Characters.Latin_1) the character referred to as a
> double-quote character is "Quotation". -- Respectively, these are
> Character'(''') and Character'('"').

It's not an apostrophe, it's a syntax error, and it doesn't refer to any
character value.

    ''' -- apostrophe character
    ''  -- syntax error
    ""  -- empty string
    "'" -- string containing a single apostrophe

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Working, but not speaking, for JetHead Development, Inc.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"