The IF - ELSE - branching

For IF-ELSE-branching, the following control statements are used :

$IF, $ELSE, $ELSIF, $ENDIF.

The branching always begins with 

$IF <expr>

and always ends with 

$ENDIF

The control statements 

$ELSE

and 

$ELSEIF

are optional and serve to build up multiple branching.

Notice

The condition in $IF-control-block is checked by verifying the mathematical expression for “true” or “ not true” (TRUE and FALSE). To be able to use also decimal variables the jump condition is fulfilled (TRUE) if..
.. the absolute value of the mathematical expression is > or = 0.5.

Programming example 

N10 ... 
N20 $IF P1 Only if |P1| is greater or equal to 0,5, the statements 
N30 ... N30 to N50 will be executed. 
N40 
N50 
N60 $ENDIF

But the following is also possible : 

N10 ... 
N20 $IF P1 >= 0.5 Only if P1 is greater or equal to 0.5 , the state-
ments N30 to N50 will be executed. 
N30 ... 
N40 
N50 
N60 $ENDIF

or 

N10 ... 
N20 $IF P1 > P2 Only if P1 is greater than P2, the statements N30 to N50
will be executed, otherwise the statements N70 to N90 
N30 ... 
N40 ... 
N50 ... 
N60 $ELSE 
N70 ... 
N80 ... 
N90 ... 
N100 $ENDIF

These use of ELSEIF permits : 

N10 ... 
N20 $IF P1 == 0 Only if P1 is equal to 0, the statements N30 to N50
will be executed, otherwise the $ELSEIF–condition will
be checked, whether P2 >= 0.5 and accordingly N70 to
N90 or N110 to N130 will be executed. 
N30 ... 
N40 
N50 
N60 $ELSEIF P2>=0.5 The $ELSEIF-condition serves for building up
branching nesting into one another. 
N70 ... 
N80 
N90 
N100 $ELSE 
N110 ... 
N120 
N130 
N140 $ENDIF

Notice

According to the programming language C, there exists difference in the syntax between
A ssignment : P5 = 3 and
Comparison: $IF P5 == 3
For the version 2.3 and earlier ones : because in mathematical expressions always the sequence
Operator -> Term -> Operator -> Term -> etc
expected, for comparison operations, those expressions with a minus sign must be bracketed ("-" is interpreted as operator).

Programming example 

$IF P1 >= -5 wrong, because term->operator->operator->term 
$IF P1 >= [-5] right, because term->operator->term->operator->term