Pascal - C (2)

[Ruud]

Hallo allemaal,
During the conversion of my program from Pascal to C, I was more or
less able to find the C equivalent of most Pascal functions so far.
Only four gave me some real trouble. I solved them but it could be I
overlooked something.

1) In Pascal you can declare functions inside a function. AFAIK this
is not possible with C. Or am I wrong?

2) In Pascal there exists the "in" function. Example:

if (c in ['A'..'F', '0'..'9']) then { c is hexadecimal }

This can be translated like:

if ( ((c >= 'A') && (c <= 'Z'))
|| ((c >= '0') && (c <= '9'))) .... // c is hexadecimal

I just wonder if there is a more simpler solution.

3) In Pascal I can "add" lines:

Line1 = 'File size:' + sSize + ' bytes.';

My solution:

strcpy(Line1, "File size:");
strcat(Line1, sSize);
strcat(Line1, " bytes.);

Again, I just wonder if there is a more simpler solution.

4) In Pascal I can "add" just one character of another string:

Str1 = Str2 + Str3[5];

Unfortunately strcat(Str1, Str3[5]); doesn't work, I get an error
message. My solution:

Str4[0] = Str3[5];
Str4[1] = 0;
strcpy(Str1, Str2};
strcat(Str1, Str4};

It works but in this case I'm certainly not happy with the solution.
Is there a better way?

Many thanks for any comment!
--
___
/ __|__
/ / |_/ Groetjes, Ruud Baltissen
\ \__|_\
\___| http://Ruud.C64.org

[dj3vande]

In article <72**********************************@r15g2000prh. googlegroups.com>,
ro***********@yahoo.com <ro***********@yahoo.comwrote:

>On Nov 2, 1:17 pm, Eric Sosman <[e-mail]:

>[e-mail] wrote:

> strcpy(Str1, Str2);
Str1[ strlen(Str2) ] = Str3[5];
Str1[ strlen(Str2) ] = '\0';

That last line looks wrong to me; I think you want to add 1 to
strlen(Str2) before you use it as an index into Str1.

Right you are. Thanks.

Actually you need to save the result of the strlen() in the second
line, since the assignment in the second line will eliminate the NUL
in Str1.

Look more closely.
He's giving strlen one string, and modifying a different one.
dave
(made the same mistake on the first reading)

--
Dave Vandervies dj3vande at eskimo dot com
You really don't want to see Dann in full flow (unless somebody else
is the victim, of course).
--Richard Heathfield in comp.lang.c

[Eric Sosman]

ro***********@yahoo.com wrote:

On Nov 2, 1:17 pm, Eric Sosman <[e-mail]:

>[e-mail] wrote:

>>> strcpy(Str1, Str2);
Str1[ strlen(Str2) ] = Str3[5];
Str1[ strlen(Str2) ] = '\0';
That last line looks wrong to me; I think you want to add 1 to
strlen(Str2) before you use it as an index into Str1.

Right you are. Thanks.

Actually you need to save the result of the strlen() in the second
line, since the assignment in the second line will eliminate the NUL
in Str1.

Having made two mistakes already in this thread, it is with
some trepidation that I maintain you're wrong here. Look again
at the function argument ...

--
Er*********@sun.com

[robertwessel2]

On Nov 3, 4:44*pm, Eric Sosman <[e-mail]:

[e-mail] wrote:

On Nov 2, 1:17 pm, Eric Sosman <[e-mail]:

[e-mail] wrote:
* * * *strcpy(Str1, Str2);
* * * *Str1[ strlen(Str2) ] = Str3[5];
* * * *Str1[ strlen(Str2) ] = '\0';
That last line looks wrong to me; I think you want to add 1 to
strlen(Str2) before you use it as an index into Str1.
* * *Right you are. *Thanks.

Actually you need to save the result of the strlen() in the second
line, since the assignment in the second line will eliminate the NUL
in Str1.

* * *Having made two mistakes already in this thread, it is with
some trepidation that I maintain you're wrong here. *Look again
at the function argument ...

Ugh. My mistake. Too much string copying going on in this thread!

[Paul Hsieh]

On Nov 1, 1:43*pm, Ruud <[e-mail]:

Hallo allemaal,

During the conversion of my program from Pascal to C, I was more
or less able to find the C equivalent of most Pascal functions so
far. Only four gave me some real trouble. I solved them but it
could be I overlooked something.

1) In Pascal you can declare functions inside a function. AFAIK
this is not possible with C. Or am I wrong?

Correct. C does not support the concept of locally scoped or
anonymous functions. That said, locally scoped functions are rarely a
serious issue.

2) In Pascal there exists the "in" function. Example:

* *if (c in ['A'..'F', '0'..'9']) then { c is hexadecimal }

This can be translated like:

* *if ( * ((c >= 'A') && (c <= 'Z'))
* * * *|| ((c >= '0') && (c <= '9'))) .... // c is hexadecimal

I just wonder if there is a more simpler solution.

The above C translates to:

if (isalnum (c)) { ... }

The Pascal is doing something different, more like:

if (isdigit (c) || (isalpha(c) && c == toupper(c))) { ... }

Except of course none of this is strictly true since in C your program
may launch nuclear missiles towards Russia if the variable c is non-
ASCII.

3) In Pascal I can "add" lines:

* Line1 = 'File size:' + sSize + ' bytes.';

My solution:

* strcpy(Line1, "File size:");
* strcat(Line1, sSize);
* strcat(Line1, " bytes.);

Again, I just wonder if there is a more simpler solution.

C sucks for strings. You can try something like sprintf (Line1, "File
size:" "%s" " bytes", sSize); and hope you don't buffer overflow, but
you really don't have Pascal's self managed string semantics in the
core language.

Have no fear, though. You can use string libraries such as mine
http://bstring.sf.net/ to make life a whole lot better:

bformata (Line1 = bfromcstr ("File size:"), "%s bytes", sSize);

This has almost exactly the same semantic behavior as Pascal.

4) In Pascal I can "add" just one character of another string:

* Str1 = Str2 + Str3[5];

Unfortunately *strcat(Str1, Str3[5]); *doesn't work, I get an
error message. My solution:

* Str4[0] = Str3[5];
* Str4[1] = 0;
* strcpy(Str1, Str2};
* strcat(Str1, Str4};

It works but in this case I'm certainly not happy with the
solution. Is there a better way?

Well using the Better String library its just:

bconchar (Str1 = bfromcstr (bdata (Str2)), bchare (Str3, 5));

But your questions are well motivated. Bare C is just really weak for
really simple fundamental things which is trivial in most programming
languages. To learn how do this right in straight C correctly you
just have to learn all of C's weaknesses. Libraries such as mine help
tremendously just for strings, but you still kind of have to learn the
C way of doing things.

--
Paul Hsieh
http://www.pobox.com/~qed/
http://bstring.sf.net/

[dj3vande]

In article <35**********************************@a3g2000prm.g ooglegroups.com>,
Nick Keighley <ni******************@hotmail.comwrote:

>I have a reflex, as soon as I see a string of the form strn* in a post
I start to post my standard "strncpy() may not do what you expect"
reply.

strncpy does exactly what I expect; it's just not usually what I want,
so I either use something else instead or use strncpy followed by some
fixup code.

I had it all composed and ready to send when I noticed he
was using strncat(). So I pressed Discard instead of Send.
But it was close :-)

Yep. strncat is the one I always have to look up; the way it
interprets its count argument is about as unlikely as it could possibly
be without looking like it was deliberately designed to be confusing.
(But writing that post did shed some light on what it might've been
designed for.)
dave

--
Dave Vandervies dj3vande at eskimo dot com
You might have the same problem that I do, though... I've got a whole
bunch of square tuits but I can't find a file to take the corners off.
--Matt Roberds in the scary devil monastery