A (sort of) Review of Strings

• What is a string?
• Why doesn't a string show up on this picture from the book?
  • 
• Strings are an example of an Abstract Data Type.
  • An abstract data type is a data type whose properties (domain and operations) are specified independently of any particular implementation.
  • See page 596 of your book.
  • I expect you to know this definition, and what it means.
• What is the domain of a string?
  • A collection of 0 or more characters.
  • Are the quotation marks part of a string?
• What are the operations on a string?
  • Assignment (stringVar = "Hello World";)
  • Comparison (<, <=, ==, > , >=)
  • Concatenation (stringVar1 + stringVar2)
  • Input/output ( cout << stringVar)
    • getline(stream, string) is a utility function.
      • documentation
      • Normally looks for a newline character (\n),
      • But can look for any character.
    • Let's write a program that reads in a file one line at a time and prints out that line.
      • For now compile with the following flags
      • -g -O3 -std=c++14 -Wall -Wextra -Wuninitialized -pedantic -Wshadow -Weffc++ -Wunused
  • c_str()
    • This returns a c style string.
    • More on these later, but needed for system type calls (opening a file)
  • size(), length(): note these return a size_t
    • Add to the program the ability to find the shortest and longest lines.
  • find()
    • This takes a string or character,
    • And possibly a starting position.
    • Take a look at cplusplus.com.
    • returns a size_t, possibly the constant string::npos
    • Note in this case, the find function is overloaded
      • There are multiple different versions with the same name.
      • The compiler decides which to use based on the parameters.
      • Or the function signature
    • Note also, some of the parameters have default values.
      • If the user does not provide the starting position, it is assigned a value of 0.
    • It turns out there are multiple find functions, but more on that later.
    • Let's look for the word "Captain" in the lines of the poem.
  • substr()
    • Worth looking at the reference here as well.
    • Note that first argument must be less than or equal to the string length.
    • The first position in a string is 0.
    • The second argument can be very large or even string::npos, only the end of the string is returned.
    • Note string::npos is the default value of the length parameter.
    • Let's split the lines on commas.
  • at() and []
    • Returns or changes the character at a given position.
    • Valid positions are 0 through size()-1
    • at will throw an exception, whatever that is, if the position is bad.
    • [] will not throw an exception
    • Let's remove all space at the beginning of a line.
    • Let's convert entire lines to upper case.
    • Let's print out only the punctuation in a line.
    • Let's reverse a line.
• Actually, we probably should find all of the operations (or functions)
  • Look here
  • This isn't everything, the standard keeps changing.
  • I wouldn't expect you to know everything here.
  • But I would expect you to that this exists.
• Some other useful functions.
  • The C library contains a set of character classification functions.
    • isalpha, is alphanum, ...
    • man isalpha
    • Know that these exist.
  • The C library also has toupper and tolower
    • man toupper
    • These convert a character only.
    • AND only convert alphabet characters, others are unchanged.
    • Page 123 of your book
  • C library has atoi, atof, ...
    • Convert a string to an int, float, long, ...
    • man atoi
  • The c++ library contains some conversion functions as well
    • to_string()
      • This is c++ 11
      • Takes a numeric type and returns a string.
      • Formats are limited.
      • sprintf from C is an alternative which provides better formatting choices
      • But that is beyond the discussion for now.
    • stoi
      • Part of a family sto*
        • i - integer
        • l - long int
        • ul - unsigned long
        • f - float
        • d - double
        • ld - long dobule
      • Again it is c++11