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IF <condition> {THEN}

    <statements>

{ELSEIF <condition>

    <statements>

{ELSE 

    <statements>

ENDIF

 

This newer form of block-structured IF statement was originally introduced in BASICplus, 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 BASICplus 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.

Subtopics

ELSEIF Clauses

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