Exercises

1. Write a function ``replace'' which takes a pointer to a string as a parameter, which replaces all spaces in that string by minus signs, and delivers the number of spaces it replaced.

   Thus

   
           char *cat = "The cat sat";
           n = replace( cat );

   should set

   
           cat to "The-cat-sat"

   and

   
           n to 2.

   (unit7:functions:rep)

2. Write a program which will read in the source of a C program from its standard input, and print out all the starred items in the following statistics for the program (all as integers). (Note the comment on tab characters at the end of this specification.)

   Print out the following values:

   
     Lines:
     *  The total number of lines
     *  The total number of blank lines
           (Any lines consisting entirely of white space should be
           considered as blank lines.)
        The percentage of blank lines (100 * blank_lines / lines)
   
     Characters:
     *  The total number of characters after tab expansion
     *  The total number of spaces after tab expansion
     *  The total number of leading spaces after tab expansion
         (These are the spaces at the start of a line, before any visible
           character; ignore them if there are no visible characters.)
       The average number of
         characters per line
         characters per line ignoring leading spaces
         leading spaces per line
         spaces per line ignoring leading spaces
   
     Comments:
     *  The total number of comments in the program
     *  The total number of characters in the comments in the program
          excluding the "/*" and "*/" thenselves
       The percentage of number of comments to total lines
       The percentage of characters in comments to characters
   
     Identifiers:
       We are concerned with all the occurrences of "identifiers" in the
         program where each part of the text starting with a letter,
         and continuing with letter, digits and underscores is considered
         to be an identifier, provided that it is not
             in a comment,
             or in a string,
             or within primes.
           Note that
               "abc\"def"
           the internal escaped quote does not close the string.
           Also, the representation of the escape character is
               '\\ '
    and of prime is
               '\''
         Do not attempt to exclude the fixed words of the language,
         treat them as identifiers. Print
     *  The total number of identifier occurrences.
     *  The total number of characters in them.
       The average identifier length.
   
     Indenting:
     *  The total number of times either of the following occurs:
         a line containing a "}" is more indented than the preceding line
         a line is preceded by a line containing a "{" and is less
           indented than it.
         The "{" and "}" must be ignored if in a comment or string or
           primes, or if the other line involved is entirely comment.
       A single count of the sum of both types of error is required.

   NOTE: All tab characters ('') on input should be interpreted as multiple spaces using the rule:

   
     "move to the next modulo 8 column"
     where the first column is numbered column 0.
    col before tab | col after tab
           ---------------+--------------
                   0      |      8
                   1      |      8
                   7      |      8
                   8      |     16
                   9      |     16
                  15      |     16
                  16      |     24

   To read input a character at a time the skeleton has code incorporated to read a line at a time for you using

   
           char ch;
           ch = getchar();

   Which will deliver each character exactly as read. The "getline" function then puts the line just read in the global array of characters "linec", null terminated, and delivers the length of the line, or a negative value if end of data has been encountered.

   You can then look at the characters just read with (for example)

   
           switch( linec[0] ) {
           case ' ': /* space ..... */
                   break;
           case '\t': /* tab character .... */
                   break;
           case '\n': /* newline ... */
                   break;
           ....
           } /* end switch */

   End of data is indicated by scanf NOT delivering the value 1.

   Your output should be in the following style:

   
           Total lines                     126
           Total blank lines               3
           Total characters                3897
           Total spaces                    1844
           Total leading spaces            1180
           Total comments                  7
           Total chars in comments         234
           Total number of identifiers     132
           Total length of identifiers     606
           Total indenting errors          2

   You may gather that the above program (together with the unstarred items) forms the basis of part of your marking system! Do the easy bits first, and leave it at that if some aspects worry you. Come back to me if you think my solution (or the specification) is wrong! That is quite possible!
   (unit7:functions:type)

3. It's rates of pay again!

   Loop performing the following operation in your program:

   Read two integers, representing a rate of pay (pence per hour) and a number of hours. Print out the total pay, with hours up to 40 being paid at basic rate, from 40 to 60 at rate-and-a-half, above 60 at double-rate. Print the pay as pounds to two decimal places.

   Terminate the loop when a zero rate is encountered. At the end of the loop, print out the total pay.

   The code for computing the pay from the rate and hours is to be written as a function.

   The recommended output format is something like:

   
           Pay at 200 pence/hr for 38 hours is 76.00 pounds
           Pay at 220 pence/hr for 48 hours is 114.40 pounds
           Pay at 240 pence/hr for 68 hours is 206.40 pounds
           Pay at 260 pence/hr for 48 hours is 135.20 pounds
           Pay at 280 pence/hr for 68 hours is 240.80 pounds
           Pay at 300 pence/hr for 48 hours is 156.00 pounds
           Total pay is 928.80 pounds

   The ``program features'' checks that explicit values such as 40 and 60 appear only once, as a #define or initialised variable value. This represents good programming practice.

   (unit7:functions:pay)