Hi,
I have made an attempt at exercise 1.14 in K&R2: namely;
"Write a program to print a histogram of the frequencies of different
characters in its input."
Here is my program and the output.
#include <stdio.h>
#define HISTHEIGHT 400
int main()
{
int c, i, j, tot;
int nchars[26];
for (i = 0; i < 26; i++)
nchars[i] = 0;
tot = 0;
while ((c = getchar()) != EOF) {
if ((c - 'A') >= 0 && (c-'A') <= 26) {
nchars[c - 'A']++;
tot++;
}
else if ((c - 'a') >= 0 && (c - 'a' <=26)) {
nchars[c-'a']++;
tot++;
}
}
/* Turn into a value out of HISTHEIGHT so it will fit screen */
/* when printing character frequencies as a histogram */
for (i = 0; i < 26; i++)
nchars[i] = ( nchars[i] * HISTHEIGHT ) / tot;
for (i = HISTHEIGHT; i 0; i--) {
for (j = 0; j < 26; j++)
if (nchars[j] >= i)
printf("***");
else
printf(" ");
printf("\n");
}
printf(" A B C D E F G H I J K L M N O P Q R S T U V W X Y Z\n");
return 0;
}
*************** ************OUT PUT************ *********
[ilan@pillemer Ch1]$ ./a.out < /usr/share/dict/words
***
***
***
***
***
***
***
***
***
*** *** ***
*** *** ***
*** *** ***
*** *** ***
*** *** ***
*** *** ***
*** *** *** ****** ***
*** *** *** ****** ******
*** *** *** ****** ******
*** *** *** ****** *********
*** *** *** ****** *********
*** *** *** ****** *********
*** *** *** *** ****** *********
*** *** *** *** ****** *********
*** *** *** *** ****** *********
*** *** *** *** ****** *********
*** *** *** *** ****** *********
*** *** *** *** ****** *********
*** *** *** *** *** ****** *********
*** *** *** *** *** ****** *********
*** ********* *** *** ****** ************
*** ********* *** *** ****** ************
*** ********* *** *** ********* ************
*** ********* ****** *************** ************
*** ********* ****** *************** ************
*** ********* ********* *************** ************
*** ********* ********* *************** ************
*************** ********* *************** ************ ***
*************** ********* *************** ************ ***
*************** ********* *************** ************ ***
*************** ************ *************** ************ ***
*************** ************ *************** *** *************** *** ***
*************** ************ *************** *** *************** *** ***
*************** ************ *************** *** *************** ************
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
[ilan@pillemer Ch1]$
3  1259 
On 01 Apr 2007 08:03:04 +0200, ilan pillemer <il**@pillemer. net>
wrote:
>Hi,
I have made an attempt at exercise 1.14 in K&R2: namely;
"Write a program to print a histogram of the frequencies of different
characters in its input."
Here is my program and the output.
#include <stdio.h>
#define HISTHEIGHT 400
int main()
{
int c, i, j, tot;
int nchars[26];
for (i = 0; i < 26; i++)
nchars[i] = 0;
tot = 0;
while ((c = getchar()) != EOF) {
if ((c - 'A') >= 0 && (c-'A') <= 26) {
A couple of issues:
Not all character sets have the alphabet in consecutive
characters. For example, EBCDIC used on IBM mainframes has seven
non-alphabetic characters between I and J.
When c-'A' is equal to 26, you attempt to increment nchars[26].
There is no such element of the array. The elements run from [0] to
[25] inclusive.
nchars[c - 'A']++;
tot++;
}
else if ((c - 'a') >= 0 && (c - 'a' <=26)) {
nchars[c-'a']++;
tot++;
}
}
/* Turn into a value out of HISTHEIGHT so it will fit screen */
/* when printing character frequencies as a histogram */
for (i = 0; i < 26; i++)
nchars[i] = ( nchars[i] * HISTHEIGHT ) / tot;
An interesting interpretation of the requirement. Every other attempt
I have seen produced actual counts, not relative frequencies.
>
for (i = HISTHEIGHT; i 0; i--) {
for (j = 0; j < 26; j++)
if (nchars[j] >= i)
printf("***");
else
printf(" ");
printf("\n");
}
printf(" A B C D E F G H I J K L M N O P Q R S T U V W X Y Z\n");
return 0;
}
Remove del for email
ilan pillemer said:
Hi,
I have made an attempt at exercise 1.14 in K&R2: namely;
<snip>
while ((c = getchar()) != EOF) {
if ((c - 'A') >= 0 && (c-'A') <= 26) {
How does this program cope on IBM mainframes? Badly, I suspect.
--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999 http://www.cpax.org.uk
email: rjh at the above domain, - www.
"ilan pillemer" <il**@pillemer. netwrote in message
Hi,
I have made an attempt at exercise 1.14 in K&R2: namely;
"Write a program to print a histogram of the frequencies of different
characters in its input."
Here is my program and the output.
#include <stdio.h>
#define HISTHEIGHT 400
int main()
{
int c, i, j, tot;
int nchars[26];
for (i = 0; i < 26; i++)
nchars[i] = 0;
tot = 0;
while ((c = getchar()) != EOF) {
if ((c - 'A') >= 0 && (c-'A') <= 26) {
nchars[c - 'A']++;
tot++;
}
else if ((c - 'a') >= 0 && (c - 'a' <=26)) {
nchars[c-'a']++;
tot++;
}
}
/* Turn into a value out of HISTHEIGHT so it will fit screen */
/* when printing character frequencies as a histogram */
for (i = 0; i < 26; i++)
nchars[i] = ( nchars[i] * HISTHEIGHT ) / tot;
for (i = HISTHEIGHT; i 0; i--) {
for (j = 0; j < 26; j++)
if (nchars[j] >= i)
printf("***");
else
printf(" ");
printf("\n");
}
printf(" A B C D E F G H I J K L M N O P Q R S T U V
W X Y Z\n");
return 0;
}
*************** ************OUT PUT************ *********
[ilan@pillemer Ch1]$ ./a.out < /usr/share/dict/words
***
***
***
***
***
***
***
***
***
*** *** ***
*** *** ***
*** *** ***
*** *** ***
*** *** ***
*** *** ***
*** *** *** ****** ***
*** *** *** ****** ******
*** *** *** ****** ******
*** *** *** ****** *********
*** *** *** ****** *********
*** *** *** ****** *********
*** *** *** *** ****** *********
*** *** *** *** ****** *********
*** *** *** *** ****** *********
*** *** *** *** ****** *********
*** *** *** *** ****** *********
*** *** *** *** ****** *********
*** *** *** *** *** ****** *********
*** *** *** *** *** ****** *********
*** ********* *** *** ****** ************
*** ********* *** *** ****** ************
*** ********* *** *** ********* ************
*** ********* ****** *************** ************
*** ********* ****** *************** ************
*** ********* ********* *************** ************
*** ********* ********* *************** ************
*************** ********* *************** ************
***
*************** ********* *************** ************
***
*************** ********* *************** ************
***
*************** ************ *************** ************
***
*************** ************ *************** *** *************** ***
***
*************** ************ *************** *** *************** ***
***
*************** ************ *************** ***
*************** ************
A B C D E F G H I J K L M N O P Q R S T U V W X Y
Z
[ilan@pillemer Ch1]$
Good first attempt.
However as Richard Heathfield pointed out, this program assumes that A to Z
are contiguous in memory. On some machines that don't use ASCII this is not
the case.
So why not write a function
/*
Convert to character to index 0 - 25
Params: ch - character to convert
Returns: index, or -1 if not an upper case character.
*/
int chtoindex(char ch)
{
char *upper = "ABCDEFGHIJKLMN OPQRSTUVWYZ";
/* code here */
}
--
Free games and programming goodies. http://www.personal.leeds.ac.uk/~bgy1mm This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
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