My usage of strcmp not working properly

Question

4.00/5 (2 votes)

See more:

Please help me out. strcmp not working properly it's only return "70" even though 2 strings are diffrent.

pch contain(0.06666, 0.0333, 0.0666 and so on)
test contain ("0.0333")

C++

float ReadFile(float Elastmod[], int NumLines,float Elastmod3[])
{
ifstream myReadFile;
char inputfile[_MAX_FNAME ],
Extension[ _MAX_EXT ] = ".CSV";

_makepath(Infilename, "C:", Dir, inputfile, Extension);

 myReadFile.open("Rdm1.csv");

 char test[] = "0.0333";

 char* pch; 

char* Token; //DYNAMICALLY ASSIGN ARRAY
Token = new char[NumLines];

int i;
 if (myReadFile.is_open()) 
 {
 while (!myReadFile.eof()) 
 {

    myReadFile.ignore(256,'\n');  // to ignore first Line
	
    myReadFile.getline(Token,256,',');


    for(int i=0;i<(NumLines-1);i++)
    {
          pch = strtok (Token,",");

	  myReadFile.getline(Token,256,',');

	  Elastmod[i]= atof(pch) ;



	int result=  (strcmp (pch,test) == 0);

        if (result == 1)

	    Elastmod3[i]= atof("90");

        else if ( result == 0)

	     Elastmod3[i]= atof("70");

         else
             Elastmod3[i]= atof("888");
}
  }

 }

else
{
//cout << "Error opening file";
}

myReadFile.close();

return Elastmod3[NumLines]  ;
}

Thank you.

[edit]Code block added - OriginalGriff[/edit]

Posted 11-Dec-13 5:25am

peoria123

Updated 11-Dec-13 6:20am

Richard MacCutchan

v3

Add a Solution

4 solutions

Solution 1

Have you cout'ed pch in the loop to see what the comparisons are?

Right now you are strcmp-ing pch and test, then comparing it to zero (false) and storing it into the result. This result will always either be zero, or one, so your "if" statement will never fall to the last "else".

It seems like strcmp is returning something other than zero in each loop. I would break it out and debug it, for example:

C++

int result=  (strcmp (pch,test) == 0);
cout << "Result=" << result << endl;
cout << "Pch=" << pch << endl;
cout << "Test=" << test << endl;
cout << "Strcmp=" << (strcmp(pch,test)) << endl;

And see what exactly is being compared, I'm thinking that pch may not be what you think it is.

Posted 11-Dec-13 5:34am

Ron Beyer

v2

Comments

Sergey Alexandrovich Kryukov 11-Dec-13 11:43am

The advice makes perfect sense, my 5, but I cannot find any sense in OP's sample. In particular, please see my answer. The code hurts my eyes too much to look at in any more. :-)
—SA

Ron Beyer 11-Dec-13 11:45am

Yeah I stopped reading past the strcmp parts, I see that the rest of it makes little sense, if you want a float, why write atof("80") instead of just 80.0f?

Sergey Alexandrovich Kryukov 11-Dec-13 12:48pm

Right. Only through a deep confusion...
—SA

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Sergey Alexandrovich Kryukov · Accepted Answer · 2013-12-11T05:41:00

There is so much of misuse here, so it's hard to discuss the code seriously. I'll only show what catches my eye at first glance.

First, the documentation of strcmp tells you that you should only compare the result with 0. You need to use '>0', '<0' or '== 0'; practically, only '==0' comparison makes sense in most cases, which indicated that strings are equal or not. I have no idea what is the sense of your comparison with 0 and 1. Please see:
http://www.cplusplus.com/reference/cstring/strcmp/[^].

Now, the expressions like atof("70"), atof("80") is the total absurd. You need to get double from string, but why? This is simply 70 or 80. Please see:
http://www.cplusplus.com/reference/cstdlib/atof/[^].

Also, 70, 80, , 256, "70" or "80" are called "immediate constants". Using them makes code quite unsupportable.

And it's good to explain the purpose of you code, if you want to get some help.

—SA

nv3 · Accepted Answer · 2013-12-11T05:52:00

As Ron already pointed out, your assumption about what strcmp will return seems to be wrong. Here is what the documentation says:

CSS

Returns an integral value indicating the relationship between the strings:
A zero value indicates that both strings are equal.
A value greater than zero indicates that the first character that does not match has a greater value in str1 than in str2; And a value less than zero indicates the opposite.

So your code is probably supposed to be something like:

C++

int result = strcmp (pch, test);
    if (result > 0)
    Elastmod3[i]= 90.0;
    else if (result == 0)
    Elastmod3[i]= 70.0;
    else
        Elastmod3[i]= 888.0;

Note that I have removed the atof calls, which are just nonesense.

And while we are at it: The entire comparison with strcmp does not make much sense. You probably want to compare the float values. And in line

C++

Elastmod[i]= atof(pch) ;

you converted already pch to float. Why don't you just compare that value to another, like:

C++

float test = 0.0333;
...
float pchf = atof (pch);
...
if (pcfh > test)
    Elastmod3[i]= 90.0;
else if (pcfh == test)
Elastmod3[i]= 70.0;
else
    Elastmod3[i]= 888.0;

And one more comment: Test test on equality of two floating point values does in most cases make not much sense.

Richard MacCutchan · Accepted Answer · 2013-12-11T06:14:00

Solution 4

C++

    pch = strtok (Token,",");

myReadFile.getline(Token,256,',');

You have used strtok to get a pointer to a token in the line buffer, then you immediately read another line into the buffer so your pointer is no longer valid.

Posted 11-Dec-13 6:14am

Richard MacCutchan

Comments

nv3 11-Dec-13 12:38pm

Good catch! 5. It probably worked just accidentally by the fact that all his lines began at same position.

Richard MacCutchan 11-Dec-13 13:26pm

Yes, you can see why it 'worked', but did not give the expected answer.

Sergey Alexandrovich Kryukov 11-Dec-13 12:47pm

Right, a 5.
—SA