/*
:: dec2bin.g
::
:: Mico Loretan, February 2005
::
:: Convert a base-10 integer into a base-2 integer.
::
:: Auxilliary proc: _log2: logarithm base 2
:: Main proc: dec2bin()
*/

proc _log2(x);
	retp( ln(x)/ln(2) );
endp;


proc dec2bin(d);
/*
::	input:	d	base-10 integer, >= 0
::	output:	b	base-2  integer
*/

local b,c;

/* check for valid input -- a non-negative integer */
if ( d<0 or (round(d) ne d) );
	errorlog "Invalid input in proc dec2bin()!"; retp(miss(0,0));
endif;

b=0;	/* initialize the output variable */

if (d>0);	/* process only if d>0 */
	do until d==0;
		c=int(_log2(d)); /* take integer part of result */
		b=b+10^c;
		d=d-2^c;
	endo;
endif;

retp( b );
endp;