|
Thinking In C++. Volume 2: Practical ProgrammingComparing strings Comparing strings is inherently different from comparing numbers. Numbers have constant, universally meaningful values. To evaluate the relationship between the magnitudes of two strings, you must make a lexical comparison. Lexical comparison means that when you test a character to see if it is "greater than" or "less than" another character, you are actually comparing the numeric representation of those characters as specified in the collating sequence of the character set being used. Most often this will be the ASCII collating sequence, which assigns the printable characters for the English language numbers in the range 32 through 127 decimal. In the ASCII collating sequence, the first "character" in the list is the space, followed by several common punctuation marks, and then uppercase and lowercase letters. With respect to the alphabet, this means that the letters nearer the front have lower ASCII values than those nearer the end. With these details in mind, it becomes easier to remember that when a lexical comparison that reports s1 is "greater than" s2, it simply means that when the two were compared, the first differing character in s1 came later in the alphabet than the character in that same position in s2 ...» |
Код для вставки книги в блог HTML
phpBB
текст
|
|