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Answer to Exercise 4-14, page 91 Solutions by Gregory Pietsch and Lars Wirzenius Define a macro swap(t,x,y) that interchanges two arguments of type t . (Block structure will help.) Here are Greg's solutions for Cat 0 and Cat 1: /* EXERCISE 4-14 Gregory Pietsch */ /* conditional compilation added by RJH */ #ifdef CATEGORY_0 #define swap(t,x,y) do{t z=x;x=y;y=z}while(0) #else #ifdef CATEGORY_1 /* ..

Answer to Exercise 4-13, page 88 Solution by Gregory Pietsch Write a recursive version of the function reverse(s) , which reverses the string s in place. /* EXERCISE 4-13 Gregory Pietsch */ static void swap(char *a, char *b, size_t n) { while (n--) { *a ^= *b; *b ^= *a; *a ^= *b; a++; b++; } } void my_memrev(char *s, size_t n) { switch (n) { case 0: case 1: break; case 2: case 3: swap(s, s + n -..

Answer to Exercise 4-12, page 88 Solution by Gregory Pietsch Adapt the ideas of printd to write a recursive version of atoi ; that is, convert an integer into a string by calling a recursive routine. /* itoa() is non-standard, but defined on p.64 as having this prototype: void itoa(int n, char s[]) Instead of this, I thought I'd use a different prototype (one I got from the library manual of one..

Modify getop so that it doesn't need to use ungetch. Hint: use an internal static variable. Solution by Gregory Pietsch, and Liangming #include #define NUMBER '0' int getop(char *s) { int c; static int buf = EOF; if (buf != EOF && buf != ' ' && buf != '\t' && !isdigit(buf) && buf != '.') { c = buf; buf = EOF; return c; } if (buf == EOF || buf == ' ' || buf == '\t') while ((*s = c = getch()) == '..

An alternate organization uses getline to read an entire input line; this makes getch and ungetch unnecessary. Revise the calculator to use this approach. An alternate organization uses getline to read an entire input line; this makes getch and ungetch unnecessary. Revise the calculator to use this approach. Solution by Franz Fritsche. /* K&R Exercise 4-10 */ /* Franz Fritsche */ #include #inclu..

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. Solution by Franz Fritsche. (Comment: The solution is virtually identical with the solution given by Tondo/Gimpel in their C Answer Book. Alas, what can I do?) /* K&R Exercise 4-9 */ /* Franz Fritsche */ #include #define BUFSIZE 100 int b..

Answer to Exercise 4-8, page 79 Solution by Steven Huang Suppose there will never be more than one character of pushback. Modify getch and ungetch accordingly. /* K&R Exercise 4-8 */ /* Steven Huang */ #include int buf = EOF; /* buffer for ungetch */ int getch(void) /* get a (possibly pushed back) character */ { int temp; if (buf != EOF) { temp = buf; buf = EOF; } else { temp = getchar(); } retu..

Answer to Exercise 4-7, page 79 Solution by Steven Huang 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 ? /* K&R Exercise 4-7 */ /* Steven Huang */ #include #include #define BUFSIZE 100 char buf[BUFSIZE]; /* buffer for ungetch */ int bufp = 0; /* next free position in buf */ int getch(void) /* g..

Answer to Exercise 4-6, page 79 Solution by Bob Wightman 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. #include #include #include #include #include #define MAXOP 100 #define NUMBER 0 /* 4-6 these are new for this exercise*/ #define IDENTIFIER 1 #define ENDSTRING 2 /* 4-6 end of new st..

Answer to Exercise 4-5, page 79 Solution by Bob Wightman Add access to library functions like sin , exp , and pow . See in Appendix B, Section 4. #include #include #include #include #include #define MAXOP 100 #define NUMBER 0 #define IDENTIFIER 1 #define TRUE 1 #define FALSE 0 /* The new additions deal with adding functions from math.h to the calculator. In anticipation of the following exercise..