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HELP ELSEUNLESS                                    Steven Hardy Mar 1982

This introduces a second condition in an -if- or -unless- statement. The

    elseunless <CONDITION> then

is completely equivalent to:

    elseif not(<CONDITION>) then

For example:

    if <CONDITION1> then <ACTION1>
    elseunless <CONDITION2> then <ACTION2>
    else <ACTION3>

When the POP-11 system executes this -if- statement it first tests
<CONDITION1>. Unless it evaluates to -false- <ACTION1> is performed. If
<CONDITION1> is -false-, then <CONDITION2> is tested; if this is -false-
then <ACTION2> is performed, otherwise <ACTION3> is performed.

Also see:

    *IF             --- Summary of -if- statement usage
    *ELSEIF         --- The use of -elseif- in conditionals
    *UNLESS         --- Summary of -unless- statement usage
    *CONDITIONALS   --- Summary of conditional statements
    *BOOLEAN        --- Boolean values in POP-11

        Summary of POP-11 syntax

--- C.all/help/elseunless
--- Copyright University of Sussex 1992. All rights reserved. ----------