IF <condition> {THEN}

    <statements>

{ELSEIF <condition>

    <statements>

{ELSE

    <statements>

ENDIF

This newer form of block-structured IF statement was originally introduced in A-BASIC Plus, and later extended by A-Shell build 1125 to support the elseif clause. Advantages over the original if statement include:

•   No need to use colons to separate statements or ampersands to continue on to additional lines.

•   For conditions that divide more than two mutually exclusive ways, you can use as many optional elseif clauses as you need.

•   Ability to nest statements (including other IF...ENDIF or other control structures within the clauses.)

Compatability: requires /X:2 or /RC. The A-Shell implementation is compatible with the BASIC Plus version at the source code level, except for the ELSEIF clause which is an A-Shell extension.

Example

if COST < 10 then

    PAY'METHOD = PM_CASH

    PETTY'CASH -= COST

elseif COST < 100 then

    PAY'METHOD = PM_CHECK

    CHECKING'ACCOUNT -= COST

elseif COST < 1000 then

    PAY'METHOD = PM_CREDIT

else

    CALL BUY'LOTTERY'TICKET

    if TICKET = WINNER then

        CALL GET'AN'ACCOUNTANT()

    else

        CALL ROB'BANK()

    endif

endif

Comments

The compiler determines whether an if statement is of the original or new (block-structured form) by whether there is a statement following the condition prior to the end of the logical line. It is possible to insert old-style if statements into the body of new-style if..endif statements, but this goes against most tenets of style.

Once you get more than a couple of elseif clauses, you may find the conceptually-equivalent switch statement to be a better match.

Beware: elseif (one word) and else if (two words) are not equivalent! The former marks the beginning of a/another mutually exclusive conditional clause that ends with either the next elseif, else, or endif. The latter marks the beginning of an else clause, and within that clause, starts a new if statement.