Splitting a c++ string into two parts

Question

I'm trying to split a string that contains "|" into two parts.

if (size_t found = s.find("|") != string::npos) { cout << "left side = " << s.substr(0,found) << endl; cout << "right side = " << s.substr(found+1, string::npos) << endl; }

This works with "a|b", but with "a | b", it will have "| b" as the right side. Why is that? How can this be fixed?

James McNellis · Accepted Answer · 2011-04-30 21:20:26Z

14

size_t found = s.find("|") != string::npos

This is a declaration; it gets parsed as

size_t found = (s.find("|") != string::npos)

So, found will always be 1 or 0. You need to declare found outside of the condition and use some parentheses:

size_t found; if ((found = s.find("|")) != string::npos)

answered Apr 30, 2011 at 21:20

James McNellis

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6 Comments

wilhelmtell Over a year ago

Yet another operator lower than == in precedence. :p

neuromancer Over a year ago

Is there a way to put the declaration of found inside the if statement?

James Kanze Over a year ago

@wilhelmtell Not an operator. As James McNellis said, size_t found = ... is a declaration. The = is part of the grammar of the declaration, and is not an operator.

James Kanze Over a year ago

@Phenom Not immediately. But why would you want to, other than for obfuscation?

JohannesD Over a year ago

For optimal readability, I'd suggest size_t found = s.find("|"); if(found != string::npos) { ... }

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