( (assert-d D) )
( (assert-d $_) 
	(abort CouldNotParse) )

;; return a dummy variable t or t1
( (tdummy mc_t mc_t1) )
( (tdummy $_ mc_t) )

;; n-th derivative t <- expr, d^n f(t)/d^n t
( (texp (iter $op $n $f $expr)
			$res)
	(assert-d $op) (!)
	(tdummy $expr $var)
	(tderiv $n $f ($var) $var $deriv) 
	(texp (progn (setf $var $expr) $deriv) $res) )

;; 1-st derivative t <- expr, d f(t)/d t
( (texp (iter1 ($op $f | $_) $expr)
			$res)
	(texp (iter $op (real 1) $f $expr) $res) )

( (get-var ($f | $_) $f) (!) )
( (get-var $x $x)
	(atom $x) (!) )
( (get-var $_ $_)
	(abort CouldNotParse) )

;; partial n-th derivative t <- args[i], d^n f(args[0], ..., args[i-1], t, args[i+1], ..., args[k])/d^n t
( (texp (iter2 $op ($i | $_) $f (list $args_))
			$res)
	(assert-d $op)
	(map &get-var-%-2 $args_ $args)
	(nth $i $args $expr)
	(tdummy $expr $var)
	(replace-nth $i $args $var () $targs)
	(tderiv $n $f $args $var $deriv)
	(texp (progn (setf $var $expr) $deriv) $res) )

( (id $x $x) )

;; apply a predicate on a list
( (map $pred () ()) )
( (map $pred ($x | $r)
			($x1 | $r1))
	($pred $x $x1)
	(map $pred $r $r1) )

( (reverse $l1 $l2) 
	(reverse $l1 () $l2) )
( (reverse () $l $l) )
( (reverse ($h | $l1) $l2 $l3) 
	(reverse $l1 ($h | $l2) $l3) )

( (nth 1: ($h | $t) $h) (!) )
( (nth $n ($h | $t)
			$res)
	(+ $n -1: $n-1)
	(nth $n-1 $t $res) )

( (nth $_ $__ aborted)
	(abort bad_subscript) )

( (replace-nth 1: ($h | $t) $x $accum 
			$res)
	(!)
	(reverse ($x | $accum) $t $res) )

( (replace-nth $n ($h | $t) $x $accum 
			$res)
	(+ $n -1: $n-1)
	(replace-nth $n-1 $t $x ($h | $accum) $res) )

( (replace-nth $_ $__ $___ $____ aborted)
	(abort bad_subscript) )