'begin'
	'comment' 
		perform some calculations with real values and check
		the result:
				sqrt (x) * sqrt (x)
				exp ( ln (x))
				arctan (sin (x) / cos (x))

		EPS is somewhat great - change for more accuracy.
	;

	'real' 'procedure' EPS;
		EPS := '10'-5;

	'procedure' doit (x);
	'begin'
		'real' xs, xa, y, yy, xx, zz;

		xs := sign (x);
		xa := abs (x);
		xx := sqrt (xa);
		xx := xs * xx * xx;
		'if' abs (x - xx) > EPS 'then'
			vprint ("sqrt differ: ", x, xx, x - xx);
		y := x - PI * entier(x / PI);
		'if' y > PI/2 'then' y := y - PI;
		yy := arctan (sin (x) / cos (x));
		'if' abs (y - yy) > EPS 'then'
			vprint ("trig differ: ", y, yy, y - yy);
		zz := xs * exp (ln (xa));
		'if' abs (x - zz) > EPS 'then'
			vprint ("exp  differ: ", x, zz, x - zz)
	'end';

	'real' x;

	vprint ("first check...");
	'for' x := -70 'step' 7.7 'until' 70 'do' 
		doit (x);
	vprint ("second check...");
	'for' x := -7 'step' 0.3 'until' 7 'do' 
		doit (x);
	vprint ("done.")
'end'