Conditions with the if-element

To evalue subobjects depending on variables, the if-element can be used.

Syntax: $Obj=if( Condition, Obj_1, Obj_2)$

If the condition is true, the first subobject $Obj_1$ will be evalued, else, if the condition is false, the second subobject $UF_2$ will be evalued.

The following conditions $Condition$ are available ($UF_i$ are subfunctions as described for function element in section 9.7 on page ):

• $true$: the condintion is true
• $false$: the condintion is false (=not true)
• $not(Condition_1)$: the condintion is true, if the $Condition_1$ is false (respectively not true), else the condition is false
• $or( Condition_1, Condition_2)$: the condintion is true, if one or more of the conditions $Condition_1$ or $Condition_2$ are true, else the condition is false
• $and( Condition_1, Condition_2)$: the condintion is true, if both of the conditions $Condition_1$ and $Condition_2$ are true, else the condition is false
• $xor( Condition_1, Condition_2)$: the condintion is true, if exactly one of the conditions $Condition_1$ or $Condition_2$ is true, else the condition is false

• $eqInt(UF_1,UF_2)$: the condintion is true, if the rounded to an integer value of the subfunction $UF_1$ is equal to the rounded to an integer value of the subfunction $UF_2$, else the condition is false; The direct comparison of floating point numbers was rejected, because due to slightly rounding errors the condition can lead to different results on different systems.
• $lo(UF_1,UF_2)$: the condintion is true, if $UF_1$ is smaler than $UF_2$ ($UF_1<UF_2$), else the condition is false
• $gr(UF_1,UF_2)$: the condintion is true, if $UF_1$ is greater than $UF_2$ ($UF_1>UF_2$), else the condition is false

Notes: The $if$ construct is one of the most powerful programming language constructs, so it was included in the Fib multimedia description language.

Examples:

• $Obj=if( lo(x,7), Obj_1, Obj_2)$; $Obj_1$ will be evalued, if the variable $x$ is smaler than $7$, else $Obj_2$ will be evalued
• $Obj=if( and( gr( add(x, 2), 3), lo(x, 7) ), Obj_1, Obj_2)$; $Obj_1$ will be evalued, if the variable $x$ plus $2$ is greater than $3$ and $x$ is smaler than $7$ (thus if $x$ is a number betwean $1$ and $7$), else $Obj_2$ will be evalued