From thomasmoore at speakeasy.net  Tue Nov  9 23:38:43 2004
From: thomasmoore at speakeasy.net (Thomas Moore)
Date: Tue, 09 Nov 2004 23:38:43 -0800
Subject: [OCLUG-devel] math functions in  C
Message-ID: <4191C583.20401@speakeasy.net>

Hi all,

I have only been on this list for a short time but
have never seen a posting. But I will anyway. I am
not a programmer but do write small programs for
my amusement.

Here is a short C program to illustrate my
problem:



#include <stdio.h>
#include <math.h>

int main(void)
{
	double x = .7854;
	double y;
	
	y = sin(x);
	printf("sin(%f) = %f\n\n", x, y);
}

Then doing

gcc -o prog prog.c

I get the following message:


/tmp/ccZW5o7k.o(.text+0x1a): In function `main':
: undefined reference to `sin'
collect2: ld returned 1 exit status


Now, math.h refers to mathcall.h which contains
all the function prototypes. Why will this not
compile? Or more to the point, what am I doing
wrong?

Thanks.

Tom



From bao at hacom.net  Tue Nov  9 23:12:53 2004
From: bao at hacom.net (Bao C. Ha)
Date: Tue, 9 Nov 2004 23:12:53 -0800 (PST)
Subject: [OCLUG-devel] math functions in  C
In-Reply-To: <4191C583.20401@speakeasy.net>
References: <4191C583.20401@speakeasy.net>
Message-ID: <38013.192.168.0.19.1100070773.squirrel@shopping.hacom.net>

gcc -o prog prog.c -lm

You need "-lm" to link to the math library.

Bao

On Tue, November 9, 2004 11:38 pm, Thomas Moore said:
> Hi all,
>
> I have only been on this list for a short time but
> have never seen a posting. But I will anyway. I am
> not a programmer but do write small programs for
> my amusement.
>
> Here is a short C program to illustrate my
> problem:
>
>
>
> #include <stdio.h>
> #include <math.h>
>
> int main(void)
> {
>  double x = .7854;
>  double y;
>
>  y = sin(x);
>  printf("sin(%f) = %f\n\n", x, y);
> }
>
> Then doing
>
> gcc -o prog prog.c
>
> I get the following message:
>
>
> /tmp/ccZW5o7k.o(.text+0x1a): In function `main':
> : undefined reference to `sin'
> collect2: ld returned 1 exit status
>
>
> Now, math.h refers to mathcall.h which contains
> all the function prototypes. Why will this not
> compile? Or more to the point, what am I doing
> wrong?
>
> Thanks.
>
> Tom
>
>
> _______________________________________________
> OCLUG-devel mailing list -- OCLUG-devel at oclug.org
> http://mailman.oclug.org/mailman/listinfo/oclug-devel
>


-- 
Best Regards.
Bao C. Ha
Hacom OpenBrick Distributor USA http://www.hacom.net
voice: (714) 530-8817 fax: (714) 530-8818
8D66 6672 7A9B 6879 85CD 42E0 9F6C 7908 ED95 6B38



From thomasmoore at speakeasy.net  Wed Nov 10 19:12:02 2004
From: thomasmoore at speakeasy.net (Thomas Moore)
Date: Wed, 10 Nov 2004 19:12:02 -0800
Subject: [OCLUG-devel] math functions in  C
In-Reply-To: <38013.192.168.0.19.1100070773.squirrel@shopping.hacom.net>
References: <4191C583.20401@speakeasy.net>
	<38013.192.168.0.19.1100070773.squirrel@shopping.hacom.net>
Message-ID: <4192D882.7040500@speakeasy.net>

Thanks, that worked great. But, I was unable
dig that fact up from the docs. Where is it
hidden?

Tom

Bao C. Ha wrote:

>gcc -o prog prog.c -lm
>
>You need "-lm" to link to the math library.
>
>Bao
>
>




From cbsmith at gmail.com  Wed Nov 10 18:19:50 2004
From: cbsmith at gmail.com (Chris Smith)
Date: Wed, 10 Nov 2004 18:19:50 -0800
Subject: [OCLUG-devel] math functions in C
In-Reply-To: <4192D882.7040500@speakeasy.net>
References: <4191C583.20401@speakeasy.net>
	 <38013.192.168.0.19.1100070773.squirrel@shopping.hacom.net>
	 <4192D882.7040500@speakeasy.net>
Message-ID: <9ae343f5041110181948af432a@mail.gmail.com>

On Wed, 10 Nov 2004 19:12:02 -0800, Thomas Moore
<thomasmoore at speakeasy.net> wrote:
> Thanks, that worked great. But, I was unable
> dig that fact up from the docs. Where is it
> hidden?

In man pages from other systems. ;-)  Deep withing the glibc package.

When in doubt use "strings" and "grep" to figure out which library has
what you need. ;-)

-- 
Chris

From james at colannino.org  Fri Nov 19 17:51:48 2004
From: james at colannino.org (James Colannino)
Date: Fri, 19 Nov 2004 17:51:48 -0800
Subject: [OCLUG-devel] Limiting range of random numbers
Message-ID: <419EA334.6050906@colannino.org>

Hey everyone,

I'm using the following code snippet to generate suedo-random numbers:

#include <stdio.h>
#include <stdlib.h>

int random() {


    char seed;   /* random number seed */


    /* open /dev/urandom for binary read-only */

    FILE *filename;
    filename = fopen ("/dev/urandom", "rb");


    fread (&seed, 1, 1, filename);
        /* read 1 byte from /dev/urandom into seed */


    fclose (filename);


    srand (seed);   /* seeds rand() */
    int random_number = rand();


    return number;
}

It works great for me.  The only problem is, all the numbers I get are 
quite large, something like 19348382 (as an example.)  I'd like to 
restrict the possible numbers to a given range, perhaps from 0 to 10 or 
some much smaller number like that.  How would I go about this?  Thanks 
in advance.

James

From james at colannino.org  Fri Nov 19 18:09:55 2004
From: james at colannino.org (James Colannino)
Date: Fri, 19 Nov 2004 18:09:55 -0800
Subject: [OCLUG-devel] Limiting range of random numbers
In-Reply-To: <419EA334.6050906@colannino.org>
References: <419EA334.6050906@colannino.org>
Message-ID: <419EA773.1060305@colannino.org>

James Colannino wrote:

> Hey everyone,
>
> I'm using the following code snippet to generate suedo-random numbers[...]


Ok, well, after playing around a bit and trying a few random things, I 
think I managed to stumble across a possible solution.  If I return 
(number % 20) instead of just number, it seems to always give me a value 
between 0 and 19.  I'm not quite sure why this works (if someone could 
tell me how that would be great) but hey, at least it's working :)

James

From tthelin at sbcglobal.net  Fri Nov 19 18:17:45 2004
From: tthelin at sbcglobal.net (Tim Thelin)
Date: Fri, 19 Nov 2004 18:17:45 -0800
Subject: [OCLUG-devel] Limiting range of random numbers
In-Reply-To: <419EA773.1060305@colannino.org>
References: <419EA334.6050906@colannino.org> <419EA773.1060305@colannino.org>
Message-ID: <419EA949.4050309@sbcglobal.net>

James Colannino wrote:

> James Colannino wrote:
>
>> Hey everyone,
>>
>> I'm using the following code snippet to generate suedo-random 
>> numbers[...]
>
>
>
> Ok, well, after playing around a bit and trying a few random things, I 
> think I managed to stumble across a possible solution.  If I return 
> (number % 20) instead of just number, it seems to always give me a 
> value between 0 and 19.  I'm not quite sure why this works (if someone 
> could tell me how that would be great) but hey, at least it's working :)
>
> James

That's because x % y is modulo math.  The expression returns the 
remainder of x / y.

So
4 % 2 == 0
5 % 2 == 1
6 % 2 == 0

9 % 3 == 0
11 % 3 == 2

And any number X in the expression X % 20 will yield a number between 0 
and 19.

Tim