Check if one string is a prefix of another

Question

I have two strings which I\'d like to compare: String and String:. Is there a library function that would return true when passed these two strings

Answer 1

This is both efficient and convenient:

str.compare(0, pre.size(), pre) == 0

compare is fast because it uses the fast traits::compare method and doesn't have to copy any data.

Here, it will compare std::min(str.size(), pre.size()) characters but if the characters in the two ranges are equal it also checks the length of pre and returns a non-zero value if pre is longer than this.

See the documentation at cplusplus.com.

I've written a test program that uses this code to compare prefixes and strings given on the command line.