checking pointer to a string

how do i find if the first character of a pointer to a string doesnt equal a character:

Code:

---

void purge(char* check)
{
if(check[0] != "#")
{
check = strcat("#",check);
}
}

---

I'm gettting

Quote:

---

Cannot convert 'char' to 'char *' in function purge(char *)

---

'#'

But you have other problems I'll let other elaberate on.....(gotta go)

gg

you just need to change "#" to '#' and you should be good to go
[edit] Dang you codeplug :) [/edit]

1)

Code:

---

if(check[0] != "#")

---

should be

Code:

---

if(check[0] != '#')

---

2)

Code:

---

strcat("#",check);

---

What are you trying to do here? "#" points to a read only area in memory so trying to append check onto it will likely cause a seg fault.

Ok thats gone now this is what i have

Code:

---

if(check[0] != '#')
{
strcat('#',check);
}

---

I'm just trying to add and # at the begining if there isnt one.

im getting this

Quote:

---

Error E2285 .\main.cpp 116: Could not find a match for 'strcat(char,char *)' in function purge(char *)

---

>strcat('#',check);
That still won't work.

>I'm just trying to add and # at the begining if there isnt one.
Using C-style strings you prety much have no choice but to use a temporary and do things manually:

Code:

---

void
purge(
  char *check
  )
{
  if (*check != '#') {
    char *save = new char[strlen(check) + 2];
    strcpy(save, "#");
    strcat(save, check);
    strcpy(check, save);
    delete [] save;
  }
}

---

Using your function declaration, it doesn't really get better. The above function is dangerous and bug riddled, and you should avoid it if possible. If you can switch to C++ strings, things become much easier:

Code:

---

void
purge(
  string& check
  )
{
  if (check[0] != '#') {
    check = '#' + check;
  }
}

---

Or you'll just have to add parameters to the function so that the C solution can be made more safe:

Code:

---

void
purge(
  char  *check,
  size_t  size
  )
{
  if (*check != '#') {
    if (strlen(check) + 1 >= size) {
      throw "Error";
    }
    char *save = new char[strlen(check) + 2];
    strcpy(save, "#");
    strcat(save, check);
    strcpy(check, save);
    delete [] save;
  }
}

---

And so on... ;)

you lost me with that whole c++ string thing when did that come about that looks a hell of a lot easier, i havent been programming in like a year or so i think i am really out of date

>when did that come about that looks a hell of a lot easier
It is easier, and it's been an official part of the language since 1998 (though present for some time before that), not to mention the slew of string classes written by just about every C++ programmer since C with Classes. ;)

hmmm I think i remember seeing it once a while ago but every tutorial I've read it used character arrays, I read last night that that was because its not going along side the object orianted ways to use a string class like that.

>every tutorial I've read it used character arrays
They were either old or substandard. C-style strings using null terminated character arrays are error prone.

>I read last night that that was because its not going along side the object orianted ways to use a string class like that.
That's bs. If use of std::string goes against OOP then C-style strings are even worse. Can you quote what you read or provide a link so I can see it in context?

http://www.tacc.utexas.edu/services/...g/how_0483.htm

i found that site after you spoke of it

also the code you showed

Code:

---

if (check[0] != '#') {
    check = '#' + check;
  }

---

compiles but doesnt work, and I can't find a way to be able to make a string into all lower case. none of the ways in the faq work with std strings

I get the impression that these people are OO cultists who feel that it isn't OO unless everything is an inheritance hierarchy. But they are correct in saying that the standard library should be used as the foundation for higher level solutions. Nowhere do they even imply that C-style strings should be used in favor of the C++ string class because it isn't object oriented.

I must have read it wrong it was really late.

to change a string to lower case, go through the string one char at a time and use function: newString[i] = tolower(myString[i]);

to check if first is a letter you could use this function:
isalpha(myString[0])

both these functions are in <cctype>
given i havnt bothered to deal with the pointer stuff...