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--
In article <1993Jan7.082202.7901@city.cs>, mb108@cs.city.ac.uk (omo
ADELAKUN T K) writes:
|>Hi folks,
|>I need a (pseudo-)random number generator for use in a tester program
|>for a queuing system. The Eiffel libraries don't appear to have such
|>a class - that is, according to grep. I can't see anything that looks
|>like a library of binaries against I can run nm. (I'm working
|>remotely
|>from the labs and have no access to manuals.) 
|>
|>If there _is_ one I'd like to know where to find it, and if there
|>isn't
|>one I'd appreciate pointers to public-domain sources (FTP?) of such
|>classes. (I'm being a pedant for software reuse... 8-)
|>
|>
|>Thanx++,			-- Oh, dear..! That syntax!
|>Toyin.
|>

I assume you want something that's uniform in the range 0.0-1.0. What I did
was the following:

Create a class (I called it MORE_MATH since it contained some functions
missing from the MATH) class (Eiffel 2.3.4 syntax):

class MORE_MATH export

	arctangent, exp, random

feature

	exp (x: REAL): REAL is
			-- Exponential function of x.
	    external
		c_exp:REAL language "C"
	    do			
		Result := c_exp (x)
	    end; -- exp

	arctangent (x: REAL): REAL is
			-- Arctangent of x.
	    external
		c_atan:REAL language "C"
	    do			
		Result := c_atan (x)
	    end; -- arctangent

	random: REAL is
			-- Random Number generator in range 0.0-1.0.
	    external
		c_rndm: REAL language "C"
	    do			
		Result := c_rndm
	    end; -- random

end -- class MORE_MATH

Alongside of this I created a more_math.c file containing:

#include <math.h>
#include <values.h>

float c_atan();
float c_exp(), c_rndm();

float c_atan(x)
float x;
{
	return ((float) atan ((double) x));
}

float c_rndm()
{
	float f1, f2;

	f1 = random();
	f2 = MAXINT;
	return (f1/f2);
}

float c_exp(x)
float x;
{
	return (exp(x));
}

Compile the more_math.c file and create an archive file from it and add that
to the EXTERNALS section of your SDF (.eiffel) file. I'm not sure whether
the C random() function is generic Unix, but I'm fairly sure that rand() is
so you could use that instead.

		David

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	David Quarrie					CEBAF MS 12H
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