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POComparing Character Literal to Std::String in C++
 

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    <p>I would like to compare a character literal with the first element of string, to check for comments in a file. Why use a char? I want to make this into a function, which accepts a character var for the comment. I don't want to allow a string because I want to limit it to a single character in length.</p> <p>With that in mind I assumed the easy way to go would be to address the character and pass it to the std::string's compare function. However this is giving me unintended results.</p> <p>My code is as follows:</p> <pre><code>#include &lt;string&gt; #include &lt;iostream&gt; int main ( int argc, char *argv[] ) { std::string my_string = "bob"; char my_char1 = 'a'; char my_char2 = 'b'; std::cout &lt;&lt; "STRING : " &lt;&lt; my_string.substr(0,1) &lt;&lt; std::endl &lt;&lt; "CHAR : " &lt;&lt; my_char1 &lt;&lt; std::endl; if (my_string.substr(0,1).compare(&amp;my_char1)==0) std::cout &lt;&lt; "WOW!" &lt;&lt; std::endl; else std::cout &lt;&lt; "NOPE..." &lt;&lt; std::endl; std::cout &lt;&lt; "STRING : " &lt;&lt; my_string.substr(0,1) &lt;&lt; std::endl &lt;&lt; "CHAR : " &lt;&lt; my_char2 &lt;&lt; std::endl; if (my_string.substr(0,1).compare(&amp;my_char2)==0) std::cout &lt;&lt; "WOW!" &lt;&lt; std::endl; else std::cout &lt;&lt; "NOPE..." &lt;&lt; std::endl; std::cout &lt;&lt; "STRING : " &lt;&lt; my_string &lt;&lt; std::endl &lt;&lt; "STRING 2 : " &lt;&lt; "bob" &lt;&lt; std::endl; if (my_string.compare("bob")==0) std::cout &lt;&lt; "WOW!" &lt;&lt; std::endl; else std::cout &lt;&lt; "NOPE..." &lt;&lt; std::endl; } </code></pre> <p>Gives me...</p> <pre><code>STRING : b CHAR : a NOPE... STRING : b CHAR : b NOPE... STRING : bob STRING 2 : bob WOW! </code></pre> <p>Why does the function think the sub-string and character aren't the same. What's the shortest way to properly compare chars and std::string vars?</p> <p>(a short rant to <strong>avoid reclassification</strong> of my question.... feel free to skip)<br> When I say shortest I mean that out of a desire for coding eloquence. Please note, this is NOT a homework question. I am a chemical engineering Ph.D candidate and am coding as part of independent research. One of my last questions was reclassified as "homework" by user <a href="https://stackoverflow.com/users/282912/msw">msw</a> (who also made a snide remark) when I asked about efficiency, which I considered on the border of abuse. My code may or may not be reused by others, but I'm trying to make it easy to read and maintainable. I also have a bizarre desire to make my code as efficient as possible where possible. Hence the questions on efficiency and eloquence.</p>
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