27.1 Requirements

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Before we start, we need to decide what we are going to do. This is a very important step and is left out of far too many programming cycles.

This chapter's program must fulfill several requirements. First, it must be long enough to demonstrate modular programming, but at the same time short enough to fit inside a single chapter. Second, it must be complex enough to demonstrate a wide range of C++ features, but simple enough for a novice C++ programmer to understand.

Finally, it must be useful. This is not so simple to define. What's useful to one person might not be useful to another. We decided to refine this requirement and restate it as "It must be useful to C++ programmers." The program we have selected reads C++ source files and generates simple statistics on the nesting of parentheses and the ratio of comments to code lines.

The specification for our statistics program is:

 Preliminary Specification for a C++ Statistics Gathering Program Steve Oualline February 10, 2002 

The program stat gathers statistics about C++ source files and prints them. The command line is:

 stat  files  

where files is a list of source files. Example 27-1 shows the output of the program on a short test file.

Example 27-1. stat/stat.out

 1 ( 0 { 0 #include <iostream>    2 ( 0 { 0     3 ( 0 { 0 int   result;    // the result of the calculations     4 ( 0 { 0 char  oper_char; // operator the user specified     5 ( 0 { 0 int   value;     // value specified after the operator     6 ( 0 { 0     7 ( 0 { 0 int main(  )    8 ( 0 { 1 {    9 ( 0 { 1     result = 0; // initialize the result    10 ( 0 { 1    11 ( 0 { 1     // loop forever (or until break reached)   12 ( 0 { 2     while (true) {   13 ( 0 { 2    std::cout << "Result: " << result << '\n';   14 ( 0 { 2    std::cout << "Enter operator and number: ";   15 ( 0 { 2    16 ( 0 { 2    std::cin >> oper_char >> value;   17 ( 0 { 2    18 ( 0 { 2         if ((oper_char == 'q')  (oper_char == 'Q'))   19 ( 0 { 2             break;   20 ( 0 { 2    21 ( 0 { 3         if (oper_char == '+') {   22 ( 0 { 3             result += value;   23 ( 0 { 3         } else if (oper_char == '-') {   24 ( 0 { 3             result -= value;   25 ( 0 { 3         } else if (oper_char == '*') {   26 ( 0 { 3             result *= value;   27 ( 0 { 3         } else if (oper_char == '/') {   28 ( 0 { 4             if (value == 0) {   29 ( 0 { 4            std::cout << "Error:Divide by zero\n";   30 ( 0 { 4            std::cout << "   operation ignored\n";   31 ( 0 { 3             } else   32 ( 0 { 3                 result /= value;   33 ( 0 { 3         } else {   34 ( 0 { 3        std::cout << "Unknown operator " << oper_char << '\n';   35 ( 0 { 2         }   36 ( 0 { 1     }   37 ( 0 { 1     return (0);   38 ( 0 { 0 } Total number of lines: 38 Maximum nesting of (  ) : 2 Maximum nesting of {} : 4 Number of blank lines .................6 Number of comment only lines ..........1 Number of code only lines .............27 Number of lines with code and comments 4 Comment to code ratio 16.1% 

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