Programming Forums > Application Development > C++

magnus.therning · Jan 10th, 2007, 10:21 AM

How can I easily replace characters in a std::string with another character?

Basically what I'd like is something like gsub (an addition to the string class in GNU's C++ class library). But I'm stuck on the Windows platform, and strongly encouraged to use the standard libraries as far as possible.

First I tried using string::iterator and indexing, but got terribly long errors when doing that.

Now my working solution is something like

Convert it to a C-string (string::copy)
Iterate over C-string, replacing characters
Stick the C-string back into the C++-string

Is there an easier way?

DaWei · Jan 10th, 2007, 10:39 AM

Quote:

got terribly long errors

Nice, specific explanation.

. Are you replacing characters or sets of characters with characters or sets of characters of the same length, or will your substitutions require adjustments in length?

magnus.therning · Jan 10th, 2007, 10:46 AM

Quote:

Originally Posted by DaWei

Nice, specific explanation.

. Are you replacing characters or sets of characters with characters or sets of characters of the same length, or will your substitutions require adjustments in length?

LOL, yes, I know. Well, I find all errors due to type problems in STL being amazingly non-specific. Usually it's better to stare long and hard at the code rather then trying to decipher the message itself.

Anyway, what I want to do is replace all occurances of a specific character with another character. I.e. the simplest case possible.

I found that the following code works:

(Toggle Plain Text)

int pos;
while((pos = my_string.find_first_of(" ")) != std::string::npos)
  my_string[pos] = '_';

But, very C++ it isn't.

DaWei · Jan 10th, 2007, 1:03 PM

Really?

:beard:

Bench · Jan 10th, 2007, 8:57 PM

Quote:

Originally Posted by magnus.therning

I found that the following code works:

(Toggle Plain Text)

int pos;
while((pos = my_string.find_first_of(" ")) != std::string::npos)
  my_string[pos] = '_';

But, very C++ it isn't.

I'd say that this is far more 'C++' ..

(Toggle Plain Text)

    std::string my_string("The quick brown fox jumped over the lazy dog");
    std::replace( my_string.begin(), my_string.end(), 'o', '*' );

DaWei · Jan 10th, 2007, 9:10 PM

Perhaps "C++" has come to mean "elegant" or similar while I was busy pondering "Pythonic". Neither example is C or Brainfuck.

magnus.therning · Jan 13th, 2007, 5:25 AM

Quote:

Originally Posted by Bench

I'd say that this is far more 'C++' ..

(Toggle Plain Text)

    std::string my_string("The quick brown fox jumped over the lazy dog");
    std::replace( my_string.begin(), my_string.end(), 'o', '*' );

Yes, that is a lot better. Thanks!

mrynit · Jan 13th, 2007, 6:09 AM

@magnus.therning

dont do assignments in a while statment like that. the only thing that should be going on in the while(...) is a boolean test condtion.

grumpy · Jan 13th, 2007, 8:09 AM

Quote:

Originally Posted by mrynit

dont do assignments in a while statment like that. the only thing that should be going on in the while(...) is a boolean test condtion.

There is no "should" about it, unless you are working with a zealous style guide.

There is nothing technically wrong with doing an assignment within the while expression.

Non-technically, it is often viewed as bad style because it is possible to introduce unintended errors or problems with code maintenance. Particularly with careless programmers -- but careless programmers will probably not comply with style guidelines anyway.

DaWei · Jan 15th, 2007, 3:37 PM

Quote:

dont do assignments in a while statment like that. the only thing that should be going on in the while(...) is a boolean test condtion.

(Toggle Plain Text)

int i = 0;
while (i < 10)
{
   myArray [i] = i;
   ++i;
}

Please send me the code that performs this function with a boolean test.

Jan 10th, 2007, 10:21 AM	#1
magnus.therning Hobbyist Programmer Join Date: May 2006 Location: Cambridge, UK Posts: 101 Rep Power: 3	Replacing characters in std::string How can I easily replace characters in a std::string with another character? Basically what I'd like is something like gsub (an addition to the string class in GNU's C++ class library). But I'm stuck on the Windows platform, and strongly encouraged to use the standard libraries as far as possible. First I tried using string::iterator and indexing, but got terribly long errors when doing that. Now my working solution is something like Convert it to a C-string (string::copy) Iterate over C-string, replacing characters Stick the C-string back into the C++-string Is there an easier way? __________________ Don't comment bad code - rewrite it. - The Elements of Programming Style (Kernighan & Plaugher)

Jan 10th, 2007, 1:03 PM	#4
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	Really? :beard: __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

Jan 10th, 2007, 9:10 PM	#6
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	Perhaps "C++" has come to mean "elegant" or similar while I was busy pondering "Pythonic". Neither example is C or Brainfuck. __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

Jan 13th, 2007, 6:09 AM	#8
mrynit Hobbyist Programmer Join Date: Mar 2006 Location: WA, USA Posts: 343 Rep Power: 3	@magnus.therning dont do assignments in a while statment like that. the only thing that should be going on in the while(...) is a boolean test condtion. __________________ i dont know much about programming but i try to help

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Programming Forums > Application Development > C++

Replacing characters in std::string