Help a beginner - simple lowercase to uppercase and so on function

[bpascal123]

Hi,

I'm posting quite a lot, i'm learning c without any solid programming
experience. So when my code doesn't work after looking why if i can't
get to know why, I ask here and i keep on coding as well.

So below is a simple lowercase to uppercase code from a to z that
doesn't fully work. I use gcc on linux and i've tried on gcc on
Windows and the output is quite the same (however nothing is return in
djgpp windows).

In gcc linux, It takes the input but it returns it after some delay
and it adds some characters i have never seen at this stage of
learning and nowwhere since i use a computer...

I don't know if it's the right way to do this, i wish pointers
wouldn't be involved for this. I can't think of a way to do this with
functions to split actions. Once this part below works, i'd like to
add some more string functions on the model of the function (UppStrg)
below :


#include <stdio.h>
#include <string.h>

void UppStrg(char *Low, char *Upp, int cnt) ;

int main(void)
{
int n = 40 ;
char Txt1[n] ;
char Txt2[n] ;

int i ;

printf("\n\nThis program reads and converts : 1- a lower case string
into upper case : \n") ;

do
{
printf("\nEnter a lowercase string : \n") ;
scanf("%s", Txt1) ;

n = strlen(Txt1) ;

for ( i = 0 ; i <= n ; i++ )
{
if ( (Txt1 <= 'a' ) || (Txt1 >= 'z') ) /* IF checks if there
are any characters other than lowercase letters */
printf("\nThere are no lowercase letters in this string !\n\n") ;
else
UppStrg(&Txt1, &Txt2, n) ;
}

} while ( (Txt1 <= 97 ) && (Txt1 >= 123) ) ;

for ( i = 0 ; i <= n ; i++ )
putchar(Txt2) ;
printf("\n\n") ;

return 0 ;
}

/* Function that should move a lowercase letter into uppercase */

void UppStrg(char *Low, char *Upp, int cnt)
{
int i ;

for ( i = 0 ; i <= cnt ; cnt++ )
*(Upp+i) = *(Low+i) - 'a' + 'A';
}

 

[bartc]

So below is a simple lowercase to uppercase code from a to z that
doesn't fully work. I use gcc on linux and i've tried on gcc on
Windows and the output is quite the same (however nothing is return in
djgpp windows).

In gcc linux, It takes the input but it returns it after some delay
and it adds some characters i have never seen at this stage of
learning and nowwhere since i use a computer...

I don't know if it's the right way to do this, i wish pointers
wouldn't be involved for this. I can't think of a way to do this with
functions to split actions. Once this part below works, i'd like to
add some more string functions on the model of the function (UppStrg)
below :


#include <stdio.h>
#include <string.h>

void UppStrg(char *Low, char *Upp, int cnt) ;

int main(void)
{
int n = 40 ;
char Txt1[n] ;
char Txt2[n] ;

You're using variable arrays here. Not causing your problems but take a bit
more care to use.

int i ;

printf("\n\nThis program reads and converts : 1- a lower case string
into upper case : \n") ;

do
{
printf("\nEnter a lowercase string : \n") ;
scanf("%s", Txt1) ;

n = strlen(Txt1) ;

for ( i = 0 ; i <= n ; i++ )
{
if ( (Txt1 <= 'a' ) || (Txt1 >= 'z') ) /* IF checks if there
are any characters other than lowercase letters */
printf("\nThere are no lowercase letters in this string !\n\n") ;
else
UppStrg(&Txt1, &Txt2, n) ;
}

} while ( (Txt1 <= 97 ) && (Txt1 >= 123) ) ;

These 2 nested loops are a mess. Once you've detected a character is not
lower case, you want to break out of the inner loop.

The Uppstrg() functions converts a single character, or a whole string? If a
whole string, it should be outside the inner loop, with Tx1 and Txt2
arguments. If a single character, you shouldn't use "&", and you need to
rewrite UppStrg! This is mainly why the program is doing strange things.

The conditional to the outer do-while loop is meaningless. 'i' is undefined
at this point. (I'm not familiar with how scanf forces a new input line, so
I'd would read the input a little differently myself, perhaps using fgets()
or getchar())

Your for-loop is also looking at the 0-terminator of the string, which is
not necessary; make i count from 0 to <n.

void UppStrg(char *Low, char *Upp, int cnt)
{
int i ;

for ( i = 0 ; i <= cnt ; cnt++ )
*(Upp+i) = *(Low+i) - 'a' + 'A';

If you're going to assume Ascii code, then just subtract 32 from the
character code...
Usually case conversion code will work with any character, and ignore
anything not a..z or A..Z, depending which way it's going. (There are anyway
standard C functions for case-converting characters or strings.)

 

[Doug Miller]

Hi,

I'm posting quite a lot, i'm learning c without any solid programming
experience. So when my code doesn't work after looking why if i can't
get to know why, I ask here and i keep on coding as well.

So below is a simple lowercase to uppercase code from a to z that
doesn't fully work. I use gcc on linux and i've tried on gcc on
Windows and the output is quite the same (however nothing is return in
djgpp windows).

Is there some reason you don't simply use toupper() ?

 

[luserXtrog]

Hi,

I'm posting quite a lot, i'm learning c without any solid programming
experience. So when my code doesn't work after looking why if i can't
get to know why, I ask here and i keep on coding as well.

So below is a simple lowercase to uppercase code from a to z that
doesn't fully work. I use gcc on linux and i've tried on gcc on
Windows and the output is quite the same (however nothing is return in
djgpp windows).

In gcc linux, It takes the input but it returns it after some delay
and it adds some characters i have never seen at this stage of
learning and nowwhere since i use a computer...

When that happens, it means the ends of your strings (the terminating
nul) is getting snipped. Step one: check loop conditions and array
lengths.

I don't know if it's the right way to do this, i wish pointers
wouldn't be involved for this. I can't think of a way to do this with
functions to split actions.

I'd make a function to transpose one character (int tr(int)).
And then one to loop across the string calling that function
for each character. And I'd probably do it in place instead of
copying at to a new array (why would you need both?).

Once this part below works, i'd like to
add some more string functions on the model of the function (UppStrg)
below :

#include <stdio.h>
#include <string.h>

void UppStrg(char *Low, char *Upp, int cnt) ;

int main(void)
{
        int n = 40 ;
        char Txt1[n] ;
        char Txt2[n] ;

        int i ;

        printf("\n\nThis program reads and converts : 1- a lower case string
into upper case : \n") ;

        do
        {
                printf("\nEnter a lowercase string : \n") ;
                scanf("%s", Txt1) ;

                n = strlen(Txt1) ;

                for ( i = 0     ;       i <= n       ;       i++ )
                {
                        if ( (Txt1 <= 'a' )       ||      (Txt1 >= 'z') ) /* IF checks if there
are any characters other than lowercase letters */
                                printf("\nThere are no lowercase letters in this string !\n\n") ;
                        else
                                UppStrg(&Txt1, &Txt2, n) ;
                }

Your spacing makes this very difficult to read.
I don't understand why you need all that space.
I also don't understand why you're calling UppStrg
in this loop. You're incrementing the offset and
asking it to modify 40 elements starting at each position.
Every time through this loop after the first, you're
asking UppStrg to modify elements that are outside of
the bounds of the array.
UppStrg should be called once for each string.
If you need to verify that the string consists
only of lowercase characters, you can use some
kind of flag value that's set in the loop when
a bogus character is encountered and then check
after the loop whether it was set. Or you can
use some standard library functions. I recently
discovered this one:

if (strspn(s,"abcdefghijklmnopqrstuvwxyz") == strlen(s))
printf("char *s consists wholy of lowercase letters\n");

        } while ( (Txt1 <= 97 )   &&      (Txt1 >= 123) ) ;

        for ( i = 0     ;       i <= n       ;       i++ )
                putchar(Txt2) ;
        printf("\n\n") ;

        return 0 ;

}

/* Function that should move a lowercase letter into uppercase */

void UppStrg(char *Low, char *Upp, int cnt)
{
        int i ;

        for ( i = 0     ;       i <= cnt     ;       cnt++ )
                *(Upp+i) = *(Low+i) - 'a' + 'A';

}

Dude, use the array notation for strings. It's prettier.
Upp = Low - 'a' + 'A';
I don't like the arithmetic here, either. It would make more
sense to me to add the difference rather than subtracting the
sum. But better that all these (IMHO) is

char *al="abcdefghijklmnopqrstuvwxyz";
char *AL="ABCDEFGHIJKLMNOPQRSTUVWXYZ";
....
Upp = AL[strchr(al, Low) - al];

This way doesn't assume ASCII, but it assumes that you've already
made sure the string consists only of lowercase characters.
Otherwise strchr will return NULL and NULL - al is not a valid
index into the AL array.

 

[bartc]

(e-mail address removed) said:


Too much, perhaps? Not that there's a limit, but for your own
benefit it may be better to think more and post less.

Leave him be; he's single-handedly keeping this group alive it seems to me.

 

[Nick Keighley]

I'm posting quite a lot, i'm learning c without any solid programming
experience.

the only way to get the experience is to practice programming.
Though you could be a little more sytematic...

So when my code doesn't work after looking why if i can't
get to know why, I ask here and i keep on coding as well.

you could try debugging it. Looking isn't enough.

So below is a simple lowercase to uppercase code from a to z that
doesn't fully work.

I don't know if it's the right way to do this, i wish pointers
wouldn't be involved for this.

you could use arrays rather than pointers.

I can't think of a way to do this with
functions to split actions.

imagine you had a friend looking over you shoulder and you explaining
what the different steps of the program does. Or add comments to
explain
what blocks of code (not lines!) do.

So your program does the following

read a line
check the line is all lower case letters
convert each character to upper case
print the new line

that gives you four possible functions. The middle two
can also be tested on their own.

#include <assert.h>

/*returns true(1) if all the characters are lower case
and false(0) otherwise */
int is_all_lower (const char s[], int size);

/* terminates the program if is_all_lower() doesn't return the
expected
answer */
void test_is_all-lower (const char s[], int size, int expected_result)
{
/* this crashes if we don't get the expected answer */
assert (is_all_lower (s,size) == expected_answer);
}

void test (void)
{
test_is_all_lower ("abc", 3, 1);
test_is_all_lower ("Abc", 3, 0);
test_is_all_lower ("abC", 3, 0);
test_is_all_lower ("@bc", 3, 0);
test_is_all_lower ("a@c", 3, 0);
test_is_all_lower ("a", 3, 1);
}

int main (void)
{
test();
return 0;
}

Once this part below works, i'd like to
add some more string functions on the model of the function (UppStrg)
below :

#include <stdio.h>
#include <string.h>

void UppStrg(char *Low, char *Upp, int cnt) ;

int main(void)
{
        int n = 40 ;

your posts would look better on the internet if you used a smaller
indentation. Maybe 4 chatacters (my favourite) or even less.

        char Txt1[n] ;

beginning identifiers with an upper case less is an odd convention.
And using a constant like n won't work on older versions of C.

                scanf("%s", Txt1) ;

scanf() is tricky to use correctly (fgets() followed by sscanf() is
better).
But if you do use it you *must* check its return value.

                n = strlen(Txt1) ;

re-using variables for multiple purposes is a bad idea. Modern
computers
have *billions* of bytes of RAM.

                for ( i = 0     ;       i <= n       ;       i++ )

I really *hate* this. Could you use less blank space?

for (i = 0; i < n; i++)

You also had an off by one error. Suppose n is 10 your loop runs 11
times.

[code reformatted]

   if ( (Txt1 <= 'a' )  ||  (Txt1 >= 'z') )
         printf("\nThere are no lowercase letters in this string !\n\n") ;

really? What about "abcdefghijklmnopqrstuvwxyZ"? Any lower case
letters?

        } while ( (Txt1 <= 97 )   &&      (Txt1 >= 123) ) ;

you know about character constants ('a' etc) why start using integers?


<snip>

 

[bartc]

I note that you snipped (without marking the snippage of) my example

It wasn't relevant to my point.

program which, as far as I can tell without further feedback from
the OP, does exactly what he needs. He would do well to dwell upon
its simplicity, and consider why he felt the need to make his
program so complicated. Cutting out deadwood is an important skill,
and one that needs to be thought about, not just posted about.

I assumed the OP's code was a learning exercise.

 

[Richard Bos]

I'm posting quite a lot, i'm learning c without any solid programming
experience.

This is not the best idea to start with. Your own nick should give you a
hint in a more advisable direction.

So when my code doesn't work after looking why if i can't get to know
why, I ask here and i keep on coding as well.

This, by contrast, is a very bad idea. _First_ get it right, then
complicate it.

} while ( (Txt1 <= 97 ) && (Txt1 >= 123) ) ;

Comparing against unencoded ASCII values is a bad idea for more reasons
than just portability.

for ( i = 0 ; i <= cnt ; cnt++ )

Your spacing doesn't make your code any easier to read.

Richard

 

[Keith Thompson]

On 26 July, 01:23, "(e-mail address removed)"


scanf() is tricky to use correctly (fgets() followed by sscanf() is
better).
But if you do use it you *must* check its return value.

Even that isn't sufficent. scanf with a "%s" format is inherently
unsafe; it will attempt to read an arbitrarily long space-delimited
word, and store that word in an object that cannot possibly be large
enough to store all possible inputs.

[...]

I really *hate* this. Could you use less blank space?

Another style point: don't put blanks in front of your semicolons.

[...]

 

[Chris M. Thomasson]

Hi,

I'm posting quite a lot, i'm learning c without any solid programming
experience. So when my code doesn't work after looking why if i can't
get to know why, I ask here and i keep on coding as well.

So below is a simple lowercase to uppercase code from a to z that
doesn't fully work. I use gcc on linux and i've tried on gcc on
Windows and the output is quite the same (however nothing is return in
djgpp windows).

[...]
___________________________________________________________
#include <stdio.h>
#include <ctype.h>


char*
strtoupper(
char* const buf
) {
char* cur = buf;
while (*cur) {
*cur = toupper(*cur);
++cur;
}
return buf;
}


int main(void) {
char str[] = "1 plus 1 = two";
puts(strtoupper(str));
return 0;
}
___________________________________________________________

 

[bpascal123]

Hi,

I'd first say thanks for your replies.
I'd study carefully what was said here, at this time i'm not sure i
can understand everything but it should take shape with more practice
of C.
I don't spend too much time thinking before i post because it's not
certain i'll keep studying at that pace.

For the code, I think (a little late) the mistake that made it not
work (compile and return something) is about thses loops where <= n
was replaced with < n (the '\0' can't be uppercase):


main :
for ( i = 0 ; i < n ; i++ )
{
if ( (Txt1 <= 'a' ) || (Txt1

= 'z') )

printf("\nThere are no lowercase
letters in this string !\n\n") ;
else
UppStrg(&Txt1, &Txt2, n) ;
}

void UppStrg :

for ( i = 0 ; i < cnt ; i++ )
*(Upp+i) = *(Low+i) - 'a' + 'A';

With these modification, it compiles and returns uppercase letters
however not regarding if true or not "There are no lowercase letters
in this string !" in gcc linux.

In Windows djgpp it just doesn't compile unless the loop in main looks
like :

for ( i = 0 ; i < n ; i++ )
UppStrg(&Txt1, &Txt2, n) ;

Some posts above seem to tell why. I'll read them carefully again.

I'd expect this code to make upppercase a whole string and not just
one charactere entered at a time if i answer right your question. Ok,
this code is not taking many consideration such as non ascii letters
or uppercase letters... Also the non-official purpose is to put at
work my understanding of loops and functions which needs more work
regarding the time i have spent on this i think.

About the spacing : I first find it easier to spot mistakes and i have
read spacing would play a role in other languages such as python. I'm
not preparing to switch to python this way yet, i'd like a good
understanding of c maybe to program with linux os...i don't know what
i'll be able to do and when.

Thx,
Pascal Baro

 

[Morris Keesan]

Pascal, I think that you're probably using lots of tab
characters in your source, have your tab stops set to
something other than "every eight columns", and don't
realize what your code looks like when
viewed by other people. It looks like this:

for ( i = 0 ; i < n ; i++ )
{
if ( (Txt1 <= 'a' ) || (Txt1

Notice that there is a huge amount of whitespace around your
';' and "||", which makes the code extremely hard to read for
anyone used to any other C code. That's what people are complaining about.


Assuming ASCII, or some other character set where all of the lowercase
letters are contiguous, with 'a' having the lowest numeric value
and 'z' the highest,

for ( i = 0; i < n; i++ )
{
if ( (Txt1 <= 'a' ) || (Txt1 = 'z') )
printf("\nThere are no lowercase letters in this string
!\n\n") ;

For EVERY CHARACTER IN Txt1 that is not a lowercase letter, this will
print "There are no lowercase letters". Even if the call to UppStrg made
sense, and even if UppStrg were coded properly, if Txt1 contained the
string "Pascal Baro" then the loop would print, THREE TIMES, the message
"\nThere are no lowercase letters in this string !\n\n". I don't think
this
is what you want.

 

[Morris Keesan]

If I were to use a const qualified object,
in a function like that,
it would be declared in the the function body.

Why? Do you really find it more readable to be
modifying your parameters?

 

[Peter Nilsson]

If I were to use a const qualified object,
in a function like that,
it would be declared in the the function body.
Why?

#include <ctype.h>

char *
str_toupper(char *buf)
{
     char *const r = buf;

     while (*buf != '\0') {
         *buf = toupper(*buf);

This does have a problem in that plain char may be signed.

         ++buf;
     }
     return r;
}

#include <ctype.h>
char *str_toupper(char *s)
{
unsigned char *r = (void *) s;
while (*r = toupper(*r)) r++;
return s;
}

 

[lovecreatesbeauty]

Why?

The value of arguments won't be modified.
I think this was discussed here before, and you obviously know it.
I also prefer pete's methold.

This does have a problem in that plain char may be signed.

The signedness of char isn't specified.
toupper() accepts an int, so I don't see problems here

 

[Nick Keighley]

I'm not sure why. Am I missing some subtlety?

I modify parameters at every given opportunity.

why? I modify a parameter only if necessary.

That's a large part of the point of having parameters.

not in my world

I've never written a prototype with a const qualified parameter.

a good time to start!

<snip>

 

[Nick Keighley]

I'd first say thanks for your replies.
I'd study carefully what was said here, at this time i'm not sure i
can understand everything but it should take shape with more practice
of C.
I don't spend too much time thinking before i post because it's not
certain i'll keep studying at that pace.

do more thinking

For the code, I think (a little late) the mistake that made it not
work (compile and return something) is about thses loops where <= n
was replaced with < n (the '\0' can't be uppercase):

don't think, test! By which I mean, don't guess that your code works;
test it.

main :
for ( i = 0 ; i < n ; i++ )
{
if ( (Txt1 <= 'a' ) || (Txt1>= 'z') )

printf("\nThere are no lowercase
letters in this string !\n\n") ;
else
UppStrg(&Txt1, &Txt2, n) ;
}

void UppStrg :

for ( i = 0 ; i < cnt ; i++ )
*(Upp+i) = *(Low+i) - 'a' + 'A';

With these modification, it compiles and returns uppercase letters
however not regarding if true or not "There are no lowercase letters
in this string !" in gcc linux.

sorry I didn't understand that

In Windows djgpp it just doesn't compile unless the loop in main looks
like :

for ( i = 0 ; i < n ; i++ )
UppStrg(&Txt1, &Txt2, n) ;

please post the complete coce that compiles under gcc Linux but not
under Windows djgpp. At the core it's the same compiler so it *ought*
to compile on both.

Some posts above seem to tell why. I'll read them carefully again.

I'd expect this code to make upppercase a whole string and not just
one charactere entered at a time if i answer right your question.

the question was (or should have been) "does the function UppStrg()
convert a single character to upper case or does it convert the whole
string?". If it converts the entire string how many times would you
expect your code to call it? How many times does your program call it?

Ok,
this code is not taking many consideration such as non ascii letters
or uppercase letters... Also the non-official purpose is to put at
work my understanding of loops and functions which needs more work
regarding the time i have spent on this i think.

About the spacing : I first find it easier to spot mistakes

whilst making it harder for every other C programmer in the galaxy.
Please switch to a more conventional layout. It will become readable
with practice.

and i have
read spacing would play a role in other languages such as python.

well you aren't programming in Python at the moment.

I'm
not preparing to switch to python this way yet, i'd like a good
understanding of c maybe to program with linux os...i don't know what
i'll be able to do and when.

In english we have the expression "don't change horses in mid-stream".
So stick with one language until you're reasonably happy with it.
Then learn another one. The first language is the hardest.


--
Nick Keighley

"Programs must be written for people to read, and only
incidentally for machines to execute."
- Abelson & Sussman, Structure and Interpretation of Computer Programs

 

[bartc]

I modify parameters at every given opportunity.

That's a large part of the point of having parameters.

How about here:

int main(int argc, char **argv) ?

Parameters are always input data to a C function. You can modify them if
they are not quite right, or if they are doing double duty as local
variables. But usually they are left alone.

I suspect you weren't being serious however..

 

[James Kuyper]

why? I modify a parameter only if necessary.

It's a variable, for which space has already been allocated - why waste
it?. If at some point in the function I no longer need to retain it's
original value, I feel perfectly free to change that value, I only
declare it const if I see no reason to change it. However, I only change
the value if I can reasonably say that the new and old values are in
some sense different values of the same thing.

That's the same rule I apply to any other variable. I don't re-use
variables for different purposes in the same block of code; that just
leads to confusion. I count on the compiler to notice that usage of one
variable never overlaps usage of another variable, and to save space by
using the same location in memory for both variables - it's better (and
far more reliable) about noticing such things than I am.

not in my world

Nor mine.

 

[Chris M. Thomasson]

I've never worked with any code
that had a const qualified parameter.

That's your _personal_ experience; so be it.



struct foo {
int x;
};


void
foo_foo(
struct foo* const self
) {
/* [...]; */
}




What's wrong with that?