Incorrect string comparison

Question

I have a problem i cannot figure out at all!

in my program the user enters numbers to be sorted. i had to be able to sort infinity, negative infinity and the so called "Nullity" (these i defined early in the program)

if the user wants to enter infinity for example they have to enter "Pinf" into the string.

my issue is i store the users input in a std::string and then check if the string is "pinf" or "Pinf" even tho i have entered the number 3 so the string is "3", it still goes into the if statement, what have i done wrong?!

My code is below;

    string Temp;
    cin>> Temp;
    if (Temp.find("Pinf")||Temp.find("pinf")) {
        Num = Pinfinity;
    }

It thinks the if statement is true everytime.

You are using bit `|` operator instead of logic `||` operator. — Netwave, Feb 28 '14 at 17:46
Do you mean `||` instead of `|` ? The logic is incorrect if the word(s) comes first as part of the sentence. — Mahesh, Feb 28 '14 at 17:46
Apart from the incorrect operator, [read the documentation](http://en.cppreference.com/w/cpp/string/basic_string/find). — chris, Feb 28 '14 at 17:46
Ive changed it so that it uses || instead of | and still goes into the if statement — JabbaWook, Feb 28 '14 at 17:49
this was solved by changing both | to || but also i HAD to use `if (Temp == "Pinf" || Temp == "pinf") {` — JabbaWook, Feb 28 '14 at 17:54

score 2 · Answer 1 · answered Feb 28 '14 at 17:48

2

1.Error - you are using | instead of ||.

2.Error - findreturns

The position of the first character of the first match. If no matches were found, the function returns string::npos. You should change

if (Temp.find("Pinf")|Temp.find("pinf")) {

to

if ((Temp.find("Pinf") != string::npos) || (Temp.find("pinf") != string::npos)) {

answered Feb 28 '14 at 17:48

Avt

16,927
4
52
72

This does work however it is overkill for my simple needs of just checking if the string is "Pinf" or "pinf" i did give your answer a plus 1 however. Thanks for the answer – JabbaWook Feb 28 '14 at 17:53

score 1 · Accepted Answer · answered Feb 28 '14 at 17:47

1

If you are just searching for Pinf or pinf then you can use this. Note the logical or operator is ||.

 if (Temp == "Pinf" || Temp == "pinf") {

answered Feb 28 '14 at 17:47

suspectus

16,548
8
49
57

score 0 · Answer 3 · answered Feb 28 '14 at 17:46

0

| is a bitwise or operator. Use || in place of |

if ( Temp.find("Pinf") != npos || Temp.find("pinf") != npos )

answered Feb 28 '14 at 17:46

HadeS

2,020
19
36

@Mahesh because if the string is not found `find()` will return npos which is not zero. – HadeS Feb 28 '14 at 17:51
@Mahesh `if` always executes for negative values...i think you are missing something.. `if` breaks when is zero/false.. – HadeS Feb 28 '14 at 18:06

Incorrect string comparison

3 Answers3