ACL2-PC_colon__colon_FAIL.html -- ACL2 Version 6.3

### ACL2-PC::FAIL

(macro) `` cause a failure

    Major Section:  PROOF-CHECKER-COMMANDS

    Examples:
    fail
    (fail t)

    General Form:
    (fail &optional hard)

This is probably only of interest to writers of macro commands. The only function of `fail` is to fail to ``succeed''.

The full story is that `fail` and `(fail nil)` simply return `(mv nil nil state)`, while `(fail hard)` returns `(mv hard nil state)` if `hard` is not `nil`. See also `do-strict`, `do-all`, and `sequence`.