NEG_DISCH : term -> thm -> thm

SYNOPSIS
Discharges an assumption, transforming |- s ==> F into |- ~s.

DESCRIBE
When applied to a term s and a theorem A |- t, the inference rule NEG_DISCH returns the theorem A - {s} |- s ==> t, or if t is just F, returns the theorem A - {s} |- ~s.
          A |- F
   --------------------  NEG_DISCH    [special case]
      A - {s} |- ~s

          A |- t
   --------------------  NEG_DISCH    [general case]
    A - {s} |- s ==> t

FAILURE
Fails unless the supplied term has type bool.

SEEALSO  DISCH,   NOT_ELIM,   NOT_INTRO

HOL  Kananaskis 0