C++Talk.NET

Chris Mantoulidis · Guest

PROBLEM: I'm having some weird problems with string::find() (in
ParamGenerate()), but since I'm not sure if that is the source of all
bad output in my program, I'm posting least code that's compilable.

OTHER INFO: Just so you know what the program does (and so you can
give it some input to test it), at this stage I want it to break the
input into some parts. Here is the input style:

<middle param> <middle param> ...... <middle param> (<final param>)

There can be infinite <middle param>s but ONLY ONE (and optional)
<final param>. Each middle param is seperated from the others with a
space and cannot contain a column (':'). The final param is just one
and starts with a ':' and can contain any kind of character.

- MORE INFO
- here's a sample command (the column is included in the beginning)
- because a column is the start of an IRC command
- :cmad!cmad_x@host PRIVMSG #cmad :this is a test message
-
- I would like this text broken into those parts
- params[0] = "cmad!cmad_x@host"
- params[1] = "PRIVMSG"
- params[2] = "#cmad"
- params[3] = ":this is a test message"
-
- but this is not the output I get

(BTW: If I try:

params.resize(ParamCount(s));

in ParamGenerate() I get a SegFault, so I set the vector size to 1024)

Here's the program code:

#include <iostream>
#include <string>
#include <vector>

using namespace std;

string arg;
vector<string> params(1024);

/*
COMMAND IS LIKE
:user@host <CMD> <PARAMS>

and params are like

<PARAMS> = <MIDDLE PARAMS> <MIDDLE PARAMS> ... <MIDDLE PARAMS> <FINAL
PARAM>

middle params are params that contain no spaces or columns ':'

.... TO BE CONTINUED ...
*/

string RemoveLeadingColumn(const string &s) {
string s2 = s;
if (s2[0] == ':') s2.erase(0,1);
return s2;
}

int ParamCount(const string &s) {
int count=1;
string::size_type i;
for (i=0; i < s.length(); i++) {
if (s[i] == ' ' /*&& !found_column*/ )
count++;
else if (s[i] == ':' /*&& !found_column*/ ) {
return count;
}
}
return count;
}

void ParamGenerate(const string &s) {
cout << "initializing vars...n";
string::size_type first_column = s.find(':');
if (first_column == string::npos) first_column=s.length();
string::size_type white_space=0;
string::size_type last=0;
int curr_param=0;
cout << "starting search...n";
while ((white_space = s.find(' ', white_space+1)) != string::npos &&
white_space <= first_column) {
cout << "found space...n";
params[curr_param] = s.substr(last,white_space);
cout << "substring is "" << s.substr(last,white_space) << ""n";
last=white_space+1;
curr_param++;
}
params[curr_param] = s.substr(first_column,s.length());
}

int main() {

cout << "gimme a cmd:n";
getline(cin,arg,'n');

cout << "you gave me: " << arg << "n";

cout << "without leading ':' it is: " << RemoveLeadingColumn(arg) <<
"n";

if (IsAddr(RemoveLeadingColumn(arg)))
cout << "nickname: " << NickFromAddr(RemoveLeadingColumn(arg)) <<
"n";

cout << "ParamCount: " << ParamCount(RemoveLeadingColumn(arg)) <<
"n";

ParamGenerate(RemoveLeadingColumn(arg));
cout << "Params generatedn";

int what;
do {
cout << "tell me a param num: ";
cin >> what;
if (what <= ParamCount(RemoveLeadingColumn(arg)) && what >= 1)
cout << "param[" << what << "] = " << params[what-1] << "n";
else
cout << "wrong indexn";
} while (what != 0);

return 0;

}

Heinz Ozwirk · Guest

"Chris Mantoulidis" <cmad_x (AT) yahoo (DOT) com> schrieb im Newsbeitrag news:a8587dd9.0402270820.35a5ed5d (AT) posting (DOT) google.com...
: PROBLEM: I'm having some weird problems with string::find() (in
: ParamGenerate()), but since I'm not sure if that is the source of all
: bad output in my program, I'm posting least code that's compilable.

Without IsAddr and NickFromAddr this code doesn't compile, but that doesn't really matter.

: string RemoveLeadingColumn(const string &s) {
: string s2 = s;
: if (s2[0] == ':') s2.erase(0,1);
: return s2;
: }

This function removes a leading colon, not a column. This doesn't matter neither, but the name is really misleading a reader.

: void ParamGenerate(const string &s) {

You should pass the destination for the generated parameter list, too. In general, global variables are not a good idea. Don't get used to them.

: cout << "initializing vars...n";
: string::size_type first_column = s.find(':');
: if (first_column == string::npos) first_column=s.length();
: string::size_type white_space=0;
: string::size_type last=0;
: int curr_param=0;
: cout << "starting search...n";
: while ((white_space = s.find(' ', white_space+1)) != string::npos &&
: white_space <= first_column) {
: cout << "found space...n";
: params[curr_param] = s.substr(last,white_space);

The second argument to std::string::substr is the length of the requested substring, not the position of the first character beyond the end of the string. So replace substr(a,b) by substr(a,b-a).

: cout << "substring is "" << s.substr(last,white_space) << ""n";
: last=white_space+1;
: curr_param++;
: }
: params[curr_param] = s.substr(first_column,s.length());
: }
:
: int main() {
:
: cout << "gimme a cmd:n";
: getline(cin,arg,'n');
:
: cout << "you gave me: " << arg << "n";
:
: cout << "without leading ':' it is: " << RemoveLeadingColumn(arg) <<
: "n";
:
:
: if (IsAddr(RemoveLeadingColumn(arg)))

Why do you call RemoveLeadingColumn over and over again. Why don't you just remove any leading colon and save the resulting string for later use? And why do you remove a leading colon at all. Your specification does not mention it.

: cout << "nickname: " << NickFromAddr(RemoveLeadingColumn(arg)) <<
: "n";
:
: cout << "ParamCount: " << ParamCount(RemoveLeadingColumn(arg)) <<
: "n";
:
: ParamGenerate(RemoveLeadingColumn(arg));
: cout << "Params generatedn";
:
: int what;
: do {
: cout << "tell me a param num: ";
: cin >> what;
: if (what <= ParamCount(RemoveLeadingColumn(arg)) && what >= 1)

params.size() would be much faster than ParamCount(RemoveLeadingColumn(arg))

: cout << "param[" << what << "] = " << params[what-1] << "n";
: else
: cout << "wrong indexn";

0 may be a bad input, but since it is the command to stop this loop, you shouldn't print an error message.

: } while (what != 0);
:
: return 0;
:
: }

Heinz