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Computing with ioLProgrammer's GuideLanguage Reference

＃ operator   ? operator   @ operator   abs tag   add tag   align field   and tag   array tag   audio tag   backgroundColor field   bold field   border field   borderBottom field   borderColor field   borderLeft field   borderRight field   borderStyle field   borderTop field   bottom field   box tag   button tag   carat field   checkBox tag   choiceBox tag   class tag   clear tag   clientFrame tag   color field   console tag   dialog tag   div tag   do field   editable field   ellipse tag   else field   eq tag   false tag   focus field   focusOrder field   font field   for tag   format field   ge tag   gt tag   height field   hotKey field   if tag   img tag   inf tag   inline field   input tag   invalid tag   int tag   italic field   join tag   layer field   le tag   left field   limit field   line tag   lt tag   margin field   marginBottom field   marginLeft field   marginRight field   marginTop field   mod tag   mul tag   ne tag   neg tag   not tag   null tag   num tag   onClear field   onClick field   onContextClick field   onExit field   onFocus field   onGet field   onInput field   onKeyDown field   onSet field   onKeyPress field   onKeyUp field   onMouseDown field   onMouseIn field   onMouseMove field   onMouseOut field   onMouseUp field   onPull field   onPush field   onResize field   onTimer field   openLink tag   or tag   pivot field   playing field   put tag   putError tag   putLn tag   requestTransfer tag   right field   rotate field   scalar tag   scroll field   scrollPos field   selectable field   spacing field   spacingBottom field   spacingLeft field   spacingRight field   spacingTop field   span tag   split tag   sub tag   table tag   tabRow tag   then field   timer tag   top field   transfer tag   transferAbility tag   transition field   true tag   underline field   vector tag   video tag   visible field   void tag   width field   with field   wrap field   xor tag


invalid tag

Transient logic tag

Generates or tests for the value invalid.

Sample usage

<invalid> — generates the value invalid.

<invalid asdfjklasdfzxcv> — Tests the contents of the primary field and generates true since asdfjklasdfzxcv evaluates to invalid. (In this case it is not defined in the document.)

Fields

Primary field

Vector field

Optional. The primary field may contain one or more values to test against.

Behaviour

The invalid tag, when used without any field values, expresses the literal value invalid anywhere it is required.

When at least one primary field value is specified, the tag tests whether the value(s) are exactly the value invalid.

Testing for invalid is often useful for validating a result generated with unreliable user input before it is passed back to the running program.