ACL2-PC_colon__colon_ORELSE.html -- ACL2 Version 6.3

### ACL2-PC::ORELSE

(macro) `` run the first instruction; if (and only if) it ``fails'', run the `` second

    Major Section:  PROOF-CHECKER-COMMANDS

    Example:
    (orelse top (print "Couldn't move to the top"))

    General form:
    (orelse instr1 instr2)

Run the first instruction. Then if it ``fails'', run the second instruction also; otherwise, stop after the first.

This instruction ``succeeds'' if and only if either `instr1` ``succeeds'', or else `instr2` ``succeeds''. If it ``fails'', then the failure is soft.