Comparing strings c

Question

I have a question   Let s say there are two std  strings and I want to compare them  there is the option of using the compare   function of the string class but I also noticed that it is possible using simple  lt   gt     operators  both of the cases are possible even if I don t include the  lt string gt  library   Can someone explain why the compare   function exists if a comparison can be made using simple operators   btw I use Code  Blocks 13 12 here is an example of my code    include  lt iostream gt   include  lt string gt   using std  cin  using std  cout  using std  endl  using std  string  using std  getline   int main         string temp1  temp2      cout  lt  lt   Enter first word         getline  cin temp1       cout  lt  lt   Enter second word         getline  cin temp2       cout  lt  lt   First word     lt  lt  temp1  lt  lt  endl  lt  lt   Second word     lt  lt  temp2  lt  lt  endl      if  temp1  gt  temp2                cout  lt  lt   One   lt  lt  endl            if  temp1 compare temp2   lt  0                cout  lt  lt   Two   lt  lt  endl            return 0

User · Answer

string cat    cat   string human    human    cout  lt  lt  cat compare human   lt  lt  endl     This code will give -1 as a result  This is due to the first non-matching character of the compared string  h  is lower or appears after  c  in alphabetical order  even though the compared string   human  is longer than  cat     I find the return value described in cplusplus com is more accurate which are-      0    They compare equal       lt 0   Either the value of the first character that does not match is lower in the compared string  or all compared characters match but the compared string is shorter       more than 0   Either the value of the first character that does not match is greater in the compared string  or all compared characters match but the compared string is longer    Moreover  IMO cppreference com s description is simpler and so far best describe to my own experience      negative value if  this appears before the character sequence specified by the arguments  in lexicographical order      zero if both character sequences compare equivalent      positive value if  this appears after the character sequence specified by the arguments  in lexicographical order

User · Answer

Regarding the question       rdquo  can someone explain why the compare   function exists if a comparison can be made using simple operands    Relative to  lt  and     the compare function is conceptually simpler and in practice it can be more efficient since it avoids two comparisons per item for ordinary ordering  of items     As an example of simplicity  for small integer values you can write a compare function like this   auto compare  int a  int b   - gt  int   return a - b      which is highly efficient   Now for a structure  struct Foo       int a      int b      int c      auto compare  Foo const amp  x  Foo const amp  y       - gt  int       if  int const r   compare  x a  y a       return r        if  int const r   compare  x b  y b       return r        return compare  x c  y c        Trying to express this lexicographic compare directly in terms of  lt  you wind up with horrendous complexity and inefficiency  relatively speaking     With C  11  for the simplicity alone ordinary less-than comparison based lexicographic compare can be very simply implemented in terms of tuple comparison

User · Answer

compare   returns an integer  which is a measure of the difference between the two strings     A return value of 0 indicates that the two strings compare as equal   A positive value means that the compared string is longer  or the first non-matching character is greater   A negative value means that the compared string is shorter  or the first non-matching character is lower    operator   simply returns a boolean  indicating whether the strings are equal or not   If you don t need the extra detail  you may as well just use

[c++] Comparing strings, c++

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