[C Programming] Functions and Program structure

We cover solution of exercises on Functions and Program structure in book "The C program language".

Power

Longest line

Exercise 1.15. Rewrite the temperature conversion program of Section 1.2 to use a function for conversion.
Solution

Get line

Exercise 1-20. Write a program detab that replaces tabs in the input with the proper number of blanks to space to the next tab stop. Assume a fixed set of tab stops, say every n columns. Should n be a variable or a symbolic parameter?
Solution

Exercise 1-21. Write a program entab that replaces strings of blanks by the minimum number of tabs and blanks to achieve the same spacing. Use the same tab stops as for detab. When either a tab or a single blank would suffice to reach a tab stop, which should be given preference?
Solution

Exercise 1-22. Write a program to ``fold'' long input lines into two or more shorter lines after the last non-blank character that occurs before the n-th column of input. Make sure your program does something intelligent with very long lines, and if there are no blanks or tabs before the specified column.
Solution

Exercise 1-23. Write a program to remove all comments from a C program. Don't forget to handle quoted strings and character constants properly. C comments don't nest.
Solution

Exercise 1-24. Write a program to check a C program for rudimentary syntax errors like unmatched parentheses, brackets and braces. Don't forget about quotes, both single and double, escape sequences, and comments. (This program is hard if you do it in full generality.)
Solution

Exercise 4-1. Write the function strindex(s,t) which returns the position of the rightmost occurrence of t in s, or -1 if there is none.
Solution

Convert string to double

Exercise 4-2. Extend atof to handle scientific notation of the form
123.45e-6
where a floating-point number may be followed by e or E and an optionally signed exponent.
Solution

Reverse Polish calculator

Exercise 4-3. Given the basic framework, it's straightforward to extend the calculator. Add the modulus (%) operator and provisions for negative numbers.

Exercise 4-4. Add the commands to print the top elements of the stack without popping, to duplicate it, and to swap the top two elements. Add a command to clear the stack.

Exercise 4-5. Add access to library functions like sin, exp, and pow. See <math.h> in Appendix B, Section 4.

Exercise 4-6. Add commands for handling variables. (It's easy to provide twenty-six variables with single-letter names.) Add a variable for the most recently printed value.

Exercise 4-7. Write a routine ungets(s) that will push back an entire string onto the input. Should ungets know about buf and bufp, or should it just use ungetch?

Exercise 4-8. Suppose that there will never be more than one character of pushback. Modify getch and ungetch accordingly.

Exercise 4-9. Our getch and ungetch do not handle a pushed-back EOF correctly. Decide what their properties ought to be if an EOF is pushed back, then implement your design.

Exercise 4-10. An alternate organization uses getline to read an entire input line; this makes getch and ungetch unnecessary. Revise the calculator to use this approach.

Exercise 4-11. Modify getop so that it doesn't need to use ungetch. Hint: use an internal static variable.

Quick sort

Exercise 4-12. Adapt the ideas of printd to write a recursive version of itoa; that is, convert an integer into a string by calling a recursive routine.

Exercise 4-13. Write a recursive version of the function reverse(s), which reverses the string s in place.

Exercise 4-14. Define a macro swap(t,x,y) that interchanges two arguments of type t. (Block structure will help.)