Chapter 4 - Functions and Program Structure

If you are intending to attempt solutions 4-3 through 4-10, you will find testing your solution to be a somewhat less laborious task if you download the following code:

Kernighan and Ritchie's Polish calculator source

It was when he was typing up this lot that the problem of copyright first occurred to Richard Heathfield - after all, it's quite a substantial quote from the book. Fortunately for Richard, Dennis Ritchie had no objections (but he did check to make sure there wouldn't be any other verbatim quotes of comparable size!).

Ex No	Pg No	Exercise	Solution	Solved by
1	71	Write the function strrindex(s,t) , which returns the position of the rightmost occurrence of t in s , or -1 if there is none.	Listing krx401	Rick Dearman Pilcrow
2	73	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.	Listing krx402	Dann Corbit
3	79	Given the basic framework, it's straightforward to extend the calculator. Add the modulus ( % ) operator and provisions for negative numbers.	Listing krx403	Bob Wightman
4	79	Add commands to print the top element of the stack without popping, to duplicate it, and to swap the top two elements. Add a command to clear the stack.	Listing krx404	Bob Wightman
5	79	Add access to library functions like sin , exp , and pow . See <math.h> in Appendix B, Section 4.	Listing krx405	Bob Wightman
6	79	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.	Listing krx406	Cat 1 Solution by Bob Wightman Jesus Alvarez
7	79	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 ?	Listing krx407	Steven Huang
8	79	Suppose that there will never be more than one character of pushback. Modify getch and ungetch accordingly.	Listing krx408	Steven Huang Jesus Alvarez
9	79	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.	Listing krx409	Franz Fritsche Jesus Alvarez
10	79	An alternate organization uses getline to read an entire input line; this makes getch and ungetch unnecessary. Revise the calculator to use this approach.	Listing krx410	Franz Fritsche
11	83	Modify getop so that it doesn't need to use ungetch. Hint: use an internal static variable.	Listing krx411	Gregory Pietsch
12	88	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.	Listing krx412	Gregory Pietsch Jesus Alvarez
13	88	Write a recursive version of the function reverse(s) , which reverses the string s in place.	Listing krx413	Gregory Pietsch Jesus Alvarez
14	91	Define a macro swap(t,x,y) that interchanges two arguments of type t . (Block structure will help.)	Listing krx414	Gregory Pietsch, Lars Wirzenius