Exercise 7-9 (isupper - Space or time efficient)

Chapter_7     Exercise_7-8     frand

ch7-Exercises     Chapter_8

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Exercise 7-9     K&R, p. 168

Exercise 7-9. Functions like isupper() can be implemented to save space or to save time. Explore both possibilities.

CONTENTS:     isupper.c     isuppm.c     isupps.c     isuppsm.c

isupper.c         download

#include <stdio.h> // for printf(), getchar()
#include <limits.h> // for UCHAR_MAX

unsigned char ISUPPER[UCHAR_MAX];

int isUpper(unsigned char c);

int main() // time efficient, requires space for array
{
int c;

for (c = 0; c < UCHAR_MAX; c++)
{ // initialize array
if (c >= 'A' && c <= 'Z')
{ISUPPER[c] = 1;}
else {ISUPPER[c] = 0;}
}

printf("Give an unsigned char: ");
c = getchar();
printf("isUpper('%c'): %d\n", c, isUpper(c));

return 0;
}

int isUpper(unsigned char c)
{
return ISUPPER[c]; // one operation
}
/*
gcc isupper.c -o isupper
./isupper
Give an unsigned char: a
isUpper('a'): 0

./isupper
Give an unsigned char: B
isUpper('B'): 1

./isupper
Give an unsigned char: 1
isUpper('1'): 0
*/

Note:  See Exercise_7-9 on clc-wiki-kr.

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isuppm.c         download

#include <stdio.h> // for printf(), getchar()
#include <limits.h> // for UCHAR_MAX

unsigned char ISUPPER[UCHAR_MAX];

#define isUpper(c) ISUPPER[c]

int main() // macro for isupper()
{
int c;

for (c = 0; c < UCHAR_MAX; c++)
{ // initialize array
if (c >= 'A' && c <= 'Z')
{ISUPPER[c] = 1;}
else {ISUPPER[c] = 0;}
}

printf("Give an unsigned char: ");
c = getchar();
printf("isUpper('%c'): %d\n", c, isUpper(c));

return 0;
}

/*
gcc isuppm.c -o isuppm
./isuppm
Give an unsigned char: a
isUpper('a'): 0

./isuppm
Give an unsigned char: B
isUpper('B'): 1

./isuppm
Give an unsigned char: 1
isUpper('1'): 0
*/

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isupps.c         download

#include <stdio.h> // for printf(), getchar()

int isUpper(unsigned char c);

int main() // space efficient, requires time for function call
{
int c;

printf("Give an unsigned char: ");
c = getchar();
printf("isUpper('%c'): %d\n", c, isUpper(c));

return 0;
}

int isUpper(unsigned char c)
{
return c >= 'A' && c <= 'Z'; // two operations
}
/*
gcc isupps.c -o isupps
./isupps
Give an unsigned char: a
isUpper('a'): 0

./isupps
Give an unsigned char: B
isUpper('B'): 1

./isupps
Give an unsigned char: 1
isUpper('1'): 0
*/

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isuppsm.c         download

#include <stdio.h> // for printf(), getchar()

#define isUpper(x) ((unsigned)((unsigned char)(x) - 'A') <= 'Z'-'A')

int main() // macro for isupper()
{
int c;

printf("Give an unsigned char: ");
c = getchar();
printf("isUpper('%c'): %d\n", c, isUpper(c));

return 0;
}

/*
gcc isuppsm.c -o isuppsm
./isuppsm
Give an unsigned char: a
isUpper('a'): 0

./isuppsm
Give an unsigned char: B
isUpper('B'): 1

./isuppsm
Give an unsigned char: 1
isUpper('1'): 0
*/

Note:  See the Macro_definition_of_isupper on StackOverflow.

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Chapter_7     Exercise_7-8     frand

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