define statement of double negation as system s infer all metavar var a end metavar indeed all metavar var b end metavar indeed not metavar var b end metavar imply not metavar var a end metavar infer not metavar var b end metavar imply metavar var a end metavar infer metavar var b end metavar end define
define proof of double negation as rule tactic end define
The pyk compiler, version 0.grue.20060417+ by Klaus Grue,