how to compare string to multiple char c++ [closed] - c++

Question

Closed. This question needs details or clarity. It is not currently accepting answers.
Want to improve this question? Add details and clarify the problem by editing this post.
Closed 8 years ago.
Improve this question
I'm trying to find out whether a string has words in it
if( mystring[i] == 'a' | 'b' | 'c' | 'd' | 'e' |)
// do stuff but it always does stuff no matter that mystring[i] is.
is always evaluating to true even if mystring[i] = a space or a period
I tried to use strcmp but I couldn't get that working right. I want it to evaluate true
only if it = a letter.

Answer 1

You cannot compare multiple values like that. Use a switch statement instead:
switch( mystring[i] )
{
case 'a':
case 'b':
case 'c':
case 'd':
case 'e':
{
// do something
break;
}
default:
{
// do something else
break;
}
}
In C/C++, if a case block does not have a break then its execution will continue in the next case block. Thus, all 5 values will execute the same // do something code. Some languages do not do that.
Another option, only because your values are consecutive, is to use this:
char ch = mystring[i];
if( (ch >= 'a') && (ch <= 'e') )
{
// do something
}
else
{
// do something else
}

Answer 2

There are two issues in your code. First, due to precedence, your expression is being evaluated as:
(mystring[i] == 'a') | ('b') | ('c') | ('d') | ('e')
Second you are using bitwise-or instead of logical-or. What you want to do is have a full condition as each term and switch to logical or:
char c = mystring[i];
if (c == 'a' || c == 'b' || c == 'c' ...)
Finally, if you are planning to check for every lower case letter, the standard library has an islower method which can check that:
if (islower(mystring[i])