counting within a string

[pkirk25]

string s =
"2631:3000:3292 :3610:3800:4333 :5294:5698:6000 :6398x3:7906:15 000:16666x2:186 15:20000"

I need to split it, make ints and get the median of the numbers.

Ideal first step is to count instances of ":"

for (a = 0; a != s.length(); ++a)
{
if (s[i] = ":") cout << a << endl;
}

Error: error C2440: '=' : cannot convert from 'const char [2]' to
'char

So my questions are - is this the best way to count elements on a
string and what is the correct incantation for s[i] where i refers to
the position int he string s?

[Victor Bazarov]

Re: counting within a string

pkirk25 wrote:

string s =
"2631:3000:3292 :3610:3800:4333 :5294:5698:6000 :6398x3:7906:15 000:16666x2:186 15:20000"
>
I need to split it, make ints and get the median of the numbers.
>
Ideal first step is to count instances of ":"
>
for (a = 0; a != s.length(); ++a)
{
if (s[i] = ":") cout << a << endl;
}
>
Error: error C2440: '=' : cannot convert from 'const char [2]' to
'char
>
So my questions are - is this the best way to count elements on a
string and what is the correct incantation for s[i] where i refers to
the position int he string s?

You might get your stuff working if you use 'istringstream' and input from
it in a loop: a number, then a char, then again a number, and so on until
the
end of the stream.

V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask

[pkirk25]

Re: counting within a string

I'm new to C++. Do you mind showing a simple example , say finding the
letter "a" in "cat" using cat as an STL strign as your start point? I
can't work out how to get form s[i] to the new tyoe of varibale you are
referring to.

[Peter Jansson]

Re: counting within a string

pkirk25 wrote:

I'm new to C++. Do you mind showing a simple example , say finding the
letter "a" in "cat" using cat as an STL strign as your start point? I
can't work out how to get form s[i] to the new tyoe of varibale you are
referring to.
>

(Personal view: Please quote somewthing of the orginal message when
replying, it is much easier to understand you.)

A simple example program follows:

#include <iostream>
#include <sstream>
#include <string>
int main()
{
// Example of construction of an istringstream:
std::istringstr eam iss(std::string ("cat"));
// Example on how to read from the istringstream:
char ch;
while(iss>>ch)
{
std::cout<<"Fou nd a char: '"<<ch<<"'."
<<(ch=='a'?" Hey, it was an 'a'!":"")<<'\n' ;
}
}


This outputs on my computer:

Found a char: 'c'.
Found a char: 'a'. Hey, it was an 'a'!
Found a char: 't'.


Sincerely,

Peter Jansson

http://www.p-jansson.com/

http://www.jansson.net/

[Michael]

Re: counting within a string

Ideal first step is to count instances of ":"
>
for (a = 0; a != s.length(); ++a)
{
if (s[i] = ":") cout << a << endl;
}
>
Error: error C2440: '=' : cannot convert from 'const char [2]' to
'char
>
So my questions are - is this the best way to count elements on a
string and what is the correct incantation for s[i] where i refers to
the position int he string s?

To answer your original question:
for (unsigned int a = 0; a != s.length(); ++a)
{
if (s[a] == ':') cout << a << endl;
}

Notes: == instead of = (this caused your compiler error), single quotes
instead of double quotes, and a instead of i.

To answer the subsequent question, here's the piece of code I use to
split strings. Use it or ignore it as you will:
vector<stringsp lit(const string& s, char delimiter)
{
vector<stringre sults;

string::size_ty pe startIndex = 0;
while (true) {
string::size_ty pe pos = s.find(delimite r, startIndex);
results.push_ba ck(s.substr(sta rtIndex, pos - startIndex));
if (pos == string::npos) {
break;
}
startIndex = pos + 1;
}
return results;
}

You would call split(s, ':')

Michael

[pkirk25]

Thanks

Michael you make it look sickeningly easy!

I will take your code, make results a vector of ints and use c_str to
populate it.

Many thanks all.

[Default User]

Re: counting within a string

pkirk25 wrote:

string s =
"2631:3000:3292 :3610:3800:4333 :5294:5698:6000 :6398x3:7906:15 000:16666x
2:18615:20000"
>
I need to split it, make ints and get the median of the numbers.
>
Ideal first step is to count instances of ":"
>
for (a = 0; a != s.length(); ++a)
{
if (s[i] = ":") cout << a << endl;
}
>
Error: error C2440: '=' : cannot convert from 'const char [2]' to
'char

You are comparing the string literal ":" to a character. The correct
character comparison would be

if (s[i] = ':')

So my questions are - is this the best way to count elements on a
string

That's one way. You can also use successive calls to s.find().

and what is the correct incantation for s[i] where i refers to
the position int he string s?

What does that mean?




Brian

[pkirk25]

Re: counting within a string

Sadly, it means it was bedtime and making sure teeth were brushed and
stories read was more important than spell checking.

[BobR]

Re: counting within a string


Default User wrote in message <4ol9q7Ff69fbU1 @individual.net >...

>pkirk25 wrote:
>

>string s =
>"2631:3000:329 2:3610:3800:433 3:5294:5698:600 0:6398x3:7906:1 5000:16666x
>2:18615:2000 0"
>>[snip]

>
>You are comparing the string literal ":" to a character. The correct
>character comparison would be
>
if (s[i] = ':')

OUCH!! A comparison would be:

if( s[i] == ':' ){ /* do something */ }

<G>
--
Bob R
POVrookie