Exersixe 4-1.Write the function strrindex(s,t) , which returns the position of the rightmost occurrence of t in s , or -1 if there is none.
Exersixe 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.
Exersixe 4-3.Given the basic framework, it's straightforward to extend the calculator. Add the modulus ( % ) operator and provisions for negative numbers.
Exersixe 4-4.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.
Exersixe 4-5.Add access to library functions like sin , exp , and pow . See <math.h> in Appendix B, Section 4.
Exersixe 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.
Exersixe 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 ?
Exersixe 4-8.Suppose that there will never be more than one character of pushback. Modify getch and ungetch accordingly.
Exersixe 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.
Exersixe 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.
Exersixe 4-11.Modify getop so that it doesn't need to use ungetch. Hint: use an internal static variable.
Exersixe 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.
Exersixe 4-13.Write a recursive version of the function reverse(s) , which reverses the string s in place.
Exersixe 4-14.Define a macro swap(t,x,y) that interchanges two arguments of type t . (Block structure will help.)
最終更新：2009年11月22日 12:27
