What is the best way to check any ASCII characters between 33 to 47
exists in a char*?
exists in a char*?
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Re: Searching in char*
spl wrote:
For maximal portability use the ispunct() function. Otherwise useWhat is the best way to check any ASCII characters between 33 to 47
exists in a char*?
something like:
if (ch >= 33 && ch <= 47) /* ... */
This is of course specific to ASCII encoding. Using ispunct may be
better but that might return true for punctuation other than those
within ASCII 33 to 47, in which case you have perform further checks.
Another possibility is a switch statement:
switch (ch) {
case '!':
case '"':
case '#':
/* and so on */
default:
/* not matching */
}
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Re: Searching in char*
santosh wrote:
Oops. Didn't catch the char * bit. Use something like:spl wrote:
>>>What is the best way to check any ASCII characters between 33 to 47
>exists in a char*?
For maximal portability use the ispunct() function. Otherwise use
something like:
>
if (ch >= 33 && ch <= 47) /* ... */
bool isASCIIpunct(co nst char *restrict str) {
bool rc = false;
while (*str++) {
if (*str >= 33 && *str <= 47) {
rc = true;
break;
}
}
return rc;
}
<snip>
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Re: Searching in char*
No, this is fine only, if I search a single character, but mine is 256
character string, in that I have to find any occurance of the Ascii
characters btw 34 to 47.
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Re: Searching in char*
spl wrote:
Use a loop. See my other post.No, this is fine only, if I search a single character, but mine is 256
character string, in that I have to find any occurance of the Ascii
characters btw 34 to 47.
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Re: Searching in char*
spl wrote:Insufficiently specified... Do you need simply to determine whetherNo, this is fine only, if I search a single character, but mine is 256
character string, in that I have to find any occurance of the Ascii
characters btw 34 to 47.
at least one character in the range is present, or identify all
instances of characters in that range?
Either way, it's hardly a challenging task, and as far as I can see,
there's little benefit in trying to use any standard functions.
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Re: Searching in char*
at least one character in the range is present...Insufficiently specified... Do you need simply to determine whether
at least one character in the range is present, or identify all
instances of characters in that range?
I feel Santosh solution would be fine... but if the string goes very
lengthy, let us say more than 1000 character, then loop will go for
1000 time. So performance vice it will be slow?
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Re: Searching in char*
spl wrote:
Given a string there is no way other than a linear search for this>>>Insufficient ly specified... Do you need simply to determine whether
>at least one character in the range is present, or identify all
>instances of characters in that range?
at least one character in the range is present...
>
I feel Santosh solution would be fine... but if the string goes very
lengthy, let us say more than 1000 character, then loop will go for
1000 time. So performance vice it will be slow?
problem. I think you'll find performance to be acceptable unless the
strings are *really* large, like say dozens of megabytes. If your
string *is* really that large then it may indicate that you may need to
rethink your data structures to avoid this problem in the first place.
Also I should point out that the solution I presented involving a switch
statement does not meet your stated requirements.
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Re: Searching in char*
spl wrote:
Probably. The search could also be done using strchr(), whichI feel Santosh solution would be fine... but if the string goes very
lengthy, let us say more than 1000 character, then loop will go for
1000 time. So performance vice it will be slow?
/might/ result in a faster search depending on compiler
optimization and/or machine architecture - on the other hand a
really smart compiler might be able to arrive at those same
optimizations by examining the loop code...
--
Morris Dovey
DeSoto Solar
DeSoto, Iowa USA
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Re: Searching in char*
spl wrote:There is no alternative to a linear search in this context. One way or>>Insufficient ly specified... Do you need simply to determine whether
>at least one character in the range is present, or identify all
>instances of characters in that range?
at least one character in the range is present...
>
I feel Santosh solution would be fine... but if the string goes very
lengthy, let us say more than 1000 character, then loop will go for
1000 time. So performance vice it will be slow?
another, each character in the array will need to be examined until you
either find one of your candidates or you reach the end.
As Morris suggests, it's possible that in some contexts the str***()
functions may have been implemented using some neat platform-specific
functionality that will make them quicker than a hand-coded loop, but
generally, I'd suggest that you just take the simple approach.
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Re: Searching in char*
Morris Dovey wrote:
Actually strcspn() or strpbrk() would be more suitable for OP's statedspl wrote:
>>>I feel Santosh solution would be fine... but if the string goes very
>lengthy, let us say more than 1000 character, then loop will go for
>1000 time. So performance vice it will be slow?
Probably. The search could also be done using strchr(), which
/might/ result in a faster search depending on compiler
optimization and/or machine architecture - on the other hand a
really smart compiler might be able to arrive at those same
optimizations by examining the loop code...
requirements except for the fact that he wants to restrict the search
to ASCII characters from 33 to 47. A manual loop seems the best
solution to me.
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Re: Searching in char*
santosh wrote:
Ok. :-)A manual loop seems the best solution to me.
--
Morris Dovey
DeSoto Solar
DeSoto, Iowa USA
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Re: Searching in char*
On Mar 18, 10:08 am, spl <splender....@g mail.comwrote:#include <string.h>What is the best way to check any ASCII characters between 33 to 47
exists in a char*?
int checkFor33to47( const char *str)
{
char set[] = {33, 34, 35, 36, 37, 38, 39, 40,
41, 42, 43, 44, 45, 46, 47, 0};
char *result = strpbrk(str, set);
return result != NULL;
}
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Re: Searching in char*
#include <string.h>Maybe faster is to use a Look-Up-Table:>
int checkFor33to47( const char *str)
{
char set[] = {33, 34, 35, 36, 37, 38, 39, 40,
41, 42, 43, 44, 45, 46, 47, 0};
>
char *result = strpbrk(str, set);
return result != NULL;
}
....
char const LUT_33TO47 [] =
{
0 /* 0*/,
0 /* 1*/,
0 /* 2*/,
...
0 /* 32*/,
1 /* 33*/,
1 /* 34*/,
...
1 /* 46*/,
1 /* 47*/,
0 /* 48*/,
...
0 /*255*/
};
....
if (LUT_33TO47[(unsigned int)c])
printf("Ok, character %d is between 33 and 47\n", c);
else
printf("No, character %d is _NOT_ between 33 and 47\n", c);
....
Regards
--
MaciekL
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