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ti-basic

Syntax error on simple If Else

I get an error at the 'Else' on a TI-84 Plus. I can't figure out why this doesn't work.

I'm writing a GCD program just as an exercise in programming a TI calculator. It's recursive (or as recursive as TI-BASIC gets).

If B=0
Disp A
Else
C->B
B->remainder(A,B)
A->B
prgmGCD2
Solution

  • TI-Basic is often rather picky about the syntax of if statements.

    There are three general formats for an If statement.

    Single Statement If

    :If <boolean>
:<expression>

    Note that <expression> consists of exactly one line of code.

    Multi Statement If

    :If <boolean>
:Then
:<expresion>
:<expresion>
:End

    As opposed to the first option, this option can contain any number of lines of code after the If.

    If Else

    :If <boolean>
:Then
:<expresion>
:<expresion>
:Else
:<expresion>
:<expresion>
:End

    As with the previous option, any number of statements can be put after the If and after the Else.

    You are obviously trying to use an if else statement. The correct syntax for this is: 

    :If B
:Then
:C->B
:B->remainder(A,B)
:A->B
:prgmGCD2
:Else
:Disp A
:End