Simple Lisp

<pre>
	[roscoe ~/lisp]$ gcc -o lisp lisp.c
	[roscoe ~/lisp]$ ./lisp example.lisp
	Bondi metric...
	Is the Einstein tensor GUU divergence-free?
	t
	&gt; (length GUU)
	280
	&gt; (length (covariant-derivative-of-up-up GUU))
	6723
	&gt; ^C
	[roscoe ~/lisp]$ ./lisp example2.lisp
	connection coefficients (p. 210)
	t
	divergence of einstein is zero (p. 222)
	t
	computing riemann tensor (p. 219)
	t
	symmetry of covariant derivative (p. 252)
	t
	covariant derivative chain rule (p. 252)
	t
	additivity of covariant derivative (p. 257)
	t
	riemann is antisymmetric on last two indices (p. 286)
	t
	riemann vanishes when antisymmetrized on last three indices (p. 286)
	t
	double dual of riemann (p. 325)
	t
	noncommutation of covariant derivatives (p. 389)
	t
	bondi metric
	t
	t
	&gt;
</pre>