CSC 107 – Programming For Science

Today’s Goal  Understand what cStrings are  Relationship to arrays & primitives  What the null character is; why we rely upon it  Know how several built-in string functions work

Today’s Goal  Understand what cStrings are  Relationship to arrays & primitives  What the null character is; why we rely upon it  Know how several built-in string functions work  Unlike “string theory”, cStrings practical & useful  Also understood by more than 10 people

Strings

What We Want  Human beings generally like using words & test  “Oh, boy! Numbers are cool” rarely, if ever, said nobody  Absolutely nobody prefers using 0 s & 1 s  Happy when using our language and not a computers

cStrings  cString  cString is special name for text-based data  Already been using cString literals  Text in quotation marks C++ treats as cString literal “Hi, Mom” “Hello world” “Good morning, Prof. Hertz. You are the greatest.” “Yes, the ‘Skins are the best football team.” “Yes! The Red Sox came back & beat the Yankees” “Wake up, Matthew. You were dreaming again”

Strings

It Is Like String Theory!

Using a cString  Remember: cString simply array of characters  Any legal use of char array okay for cString char bob[4] = “Bob”; char longStr[20] = “This is very long.”; char reallyLong[10000] = “Dummy”; char critics[] = “Statler & Waldorf”; char number[4] = “Four”; char bad[2] = “Will this compile?”; char hello[6] = {‘H’,‘e’,‘l’,‘l’,‘o’,‘\0’}; longStr = “Seventy-five”; bob = “o”; reallyLong[0] = ‘B’; bob[3] = ‘a’;

Using a cString  Remember: cString simply array of characters  Any legal use of char array okay for cString char bob[4] = “Bob”; char longStr[20] = “This is very long.”; char reallyLong[10000] = “Dummy”; char critics[] = “Statler & Waldorf”; char number[4] = “Four”; char bad[2] = “Will this compile?”; char hello[6] = {‘H’,‘e’,‘l’,‘l’,‘o’,‘\0’}; longStr = “Seventy-five”; bob = “o”; reallyLong[0] = ‘B’; bob[3] = ‘a’;

Using a cString  Remember: cString simply array of characters  Any legal use of char array okay for cString char bob[4] = “Bob”; char longStr[20] = “This is very long.”; char reallyLong[10000] = “Dummy”; char critics[] = “Statler & Waldorf”; char number[4] = “Four”; char bad[2] = “Will this compile?”; char hello[6] = {‘H’,‘e’,‘l’,‘l’,‘o’,‘\0’}; longStr = “Seventy-five”; bob = “o”; reallyLong[0] = ‘B’; bob[3] = ‘a’;

Using a cString  Remember: cString simply array of characters  Any legal use of char array okay for cString char bob[4] = “Bob”; char longStr[20] = “This is very long.”; char reallyLong[10000] = “Dummy”; char critics[] = “Statler & Waldorf”; char number[4] = “Four”; char bad[2] = “Will this compile?”; char hello[6] = {‘H’,‘e’,‘l’,‘l’,‘o’,‘\0’}; longStr = “Seventy-five”; bob = “o”; reallyLong[0] = ‘B’; bob[3] = ‘a’;

Using a cString  Remember: cString simply array of characters  Any legal use of char array okay for cString char bob[4] = “Bob”; char longStr[20] = “This is very long.”; char reallyLong[10000] = “Dummy”; char critics[] = “Statler & Waldorf”; char number[4] = “Four”; char bad[2] = “Will this compile?”; char hello[6] = {‘H’,‘e’,‘l’,‘l’,‘o’,‘\0’}; longStr = “Seventy-five”; bob = “o”; reallyLong[0] = ‘B’; bob[3] = ‘a’;

Using a cString  Remember: cString simply array of characters  Any legal use of char array okay for cString char bob[4] = “Bob”; char longStr[20] = “This is very long.”; char reallyLong[10000] = “Dummy”; char critics[] = “Statler & Waldorf”; char number[4] = “Four”; char bad[2] = “Will this compile?”; char hello[6] = {‘H’,‘e’,‘l’,‘l’,‘o’,‘\0’}; longStr = “Seventy-five”; bob = “o”; reallyLong[0] = ‘B’; bob[3] = ‘a’;

Using a cString  Remember: cString simply array of characters  Any legal use of char array okay for cString char bob[4] = “Bob”; char longStr[20] = “This is very long.”; char reallyLong[10000] = “Dummy”; char critics[] = “Statler & Waldorf”; char number[4] = “Four”; char bad[2] = “Will this compile?”; char hello[6] = {‘H’,‘e’,‘l’,‘l’,‘o’,‘\0’}; longStr = “Seventy-five”; bob = “o”; reallyLong[0] = ‘B’; bob[3] = ‘a’;

Using a cString  Remember: cString simply array of characters  Any legal use of char array okay for cString char bob[4] = “Bob”; char longStr[20] = “This is very long.”; char reallyLong[10000] = “Dummy”; char critics[] = “Statler & Waldorf”; char number[4] = “Four”; char bad[2] = “Will this compile?”; char hello[6] = {‘H’,‘e’,‘l’,‘l’,‘o’,‘\0’}; longStr = “Seventy-five”; bob = “o”; reallyLong[0] = ‘B’; bob[3] = ‘a’;

Using a cString  Remember: cString simply array of characters  Any legal use of char array okay for cString char bob[4] = “Bob”; char longStr[20] = “This is very long.”; char reallyLong[10000] = “Dummy”; char critics[] = “Statler & Waldorf”; char number[4] = “Four”; char bad[2] = “Will this compile?”; char hello[6] = {‘H’,‘e’,‘l’,‘l’,‘o’,‘\0’}; longStr = “Seventy-five”; bob = “o”; reallyLong[0] = ‘B’; bob[3] = ‘a’;

Using a cString  Remember: cString simply array of characters  Any legal use of char array okay for cString char bob[4] = “Bob”; char longStr[20] = “This is very long.”; char reallyLong[10000] = “Dummy”; char critics[] = “Statler & Waldorf”; char number[4] = “Four”; char bad[2] = “Will this compile?”; char hello[6] = {‘H’,‘e’,‘l’,‘l’,‘o’,‘\0’}; longStr = “Seventy-five”; bob = “o”; reallyLong[0] = ‘B’; bob[3] = ‘a’;

Using a cString  Remember: cString simply array of characters  Any legal use of char array okay for cString char bob[4] = “Bob”; char longStr[20] = “This is very long.”; char reallyLong[10000] = “Dummy”; char critics[] = “Statler & Waldorf”; char number[4] = “Four”; char bad[2] = “Will this compile?”; char hello[6] = {‘H’,‘e’,‘l’,‘l’,‘o’,‘\0’}; longStr = “Seventy-five”; bob = “o”; reallyLong[0] = ‘B’; bob[3] = ‘a’;

Using a cString  Remember: cString simply array of characters  Any legal use of char array okay for cString char bob[4] = “Bob”; char longStr[20] = “This is very long.”; char reallyLong[10000] = “Dummy”; char critics[] = “Statler & Waldorf”; char number[4] = “Four”; char bad[2] = “Will this compile?”; char hello[6] = {‘H’,‘e’,‘l’,‘l’,‘o’,‘\0’}; longStr = “Seventy-five”; bob = “o”; reallyLong[0] = ‘B’; bob[3] = ‘a’;

cString Input & Output  Already works with cout just int or double  This is not normal & only for array of characters  Prints all characters until null character is hit  Array’s length unknown, only stops at null character  Two possible ways to read in a cString using cin  Can read in all characters until whitespace reached  Read in at most n characters on a single line

Reading in “word” with cin  Can use cin to read in single “word”  Skips over any whitespace until finds a real character  Continues reading until it hits next whitespace  Result (& end null character) stored in cString  Caveat emptor: no check that array has enough space char lastName[80]; cin >> lastName; char middleName[2]; cin >> middleName;

Reading in Line with cin  Can use cin to read in up to an entire line  Where last cin statement stopped, this call will start  Continues reading until it hits end of the line  Result (& end null character) stored in cString  No worries: includes maximum characters to read char lastName[80]; cin.getline(lastName, 80); char middleInitial[2]; cin.getline(middleName, 2);

Built-in String Functions  To use built-in string function, your program needs: #include #include  Many, many function exist for you to use  Several of these listed on page 311 of book  Special feature of cStrings used by these functions  Unlike other arrays, can pass cString literals to functions char str[10] = “c”; str = “b”; strcat(str, “at”); cout << strlen(“Hi mom.”);

Built-in String Functions  To use built-in string function, your program needs: #include #include  Many, many function exist for you to use  Several of these listed on page 311 of book  Special feature of cStrings used by these functions  Unlike other arrays, can pass cString literals to functions char str[10] = “c”; str = “b”; strcat(str, “at”); cout << strlen(“Hi mom.”);

Important String Functions  strlen(s)  Counts characters in s before null character  strcpy(s,t)  Copies characters in t into s.  strcat(s,t)  Appends t to end of s.  strcmp(s,t)  Returns negative int if s t, and 0 if s==t  strupr(s)  Converts all characters in s to uppercase  strlwr(s)  Converts all characters in s to lowercase  strncpy(s,t,n)  Copied first n characters from t to s  stricmp(s,t)  Like strcmp, but treats upper & lowercase characters as equals

Using String Functions char cat[100] = “ca”; int i; i = strlen(cat); cat[2] = ‘t’; i = strlen(cat); strcpy(cat, “dog”); cout << cat << endl; strcat(cat, “ged”); cout << cat << endl; strcpy(cat, “ca”); cat[2] = ‘t’; cat[3] = ‘\0’; cout << cat << endl;

Using String Functions char cat[100] = “cat” char str[100] = “apult”; strcat(cat, str); cout << cat << “ ” << str << endl; cout << strcmp(cat, str) << endl; cat[0] = ‘C’; cout << strcmp(cat, “catapult”) << endl; cout << stricmp(cat, “catapult”) << endl; cat[1] = ‘\0’; strcat(str, cat); cout << cat << “ ” << str << endl;

Your Turn  Get into your groups and try this assignment

For Next Lecture  Multidimensional arrays in Section –  What do these arrays look like?  How can we create pictures & bridges in C++?  How much cooler can arrays get?  Angel also has Weekly Assignment #9 due today  Programming Assignment #2 due on Friday