How is this possible?

Question

Let me share with you the results of this code snippet 
 a!map( length: length(local!taller.resultado.contractSetting.annuitySettings.paymentMethods), pm: local!taller.resultado.contractSetting.annuitySettings.paymentMethods, isnull: a!isNullOrEmpty(local!taller.resultado.contractSetting.annuitySettings.paymentMethods) )

I'm wondering why length of a null array is equal to 1. I appreciate any explanation to this. 
 Regards

juergeng0002 · Answer

Or you might utilize Stefan's rule 'isVoid' checking for empty structures (all sorts of). ri!value is of type 'Any Type' if(
 a!isNullOrEmpty(ri!value),
 true,
 a!localVariables(
 local!typeNum: a!refreshVariable(
 value: runtimetypeof(ri!value),
 refreshAlways: true
 ),

 /* Strings */
 if(
 local!typeNum = 'type!{http://www.appian.com/ae/types/2009}Text',
 /* Ignore white space */
 len(trim(ri!value)) = 0,

 /* List of Variant */
 if(
 local!typeNum = 'type!{http://www.appian.com/ae/types/2009}Variant?list',
 all(a!isNullOrEmpty(_), a!flatten(ri!value)),

 /* Lists */
 if(
 /* Try to take first item in list and cast it to a list of itself */
 /* then compare its datatype to the incoming data type */
 local!typeNum = runtimetypeof(cast(runtimetypeof({index(ri!value, 1, null)}), ri!value)),

 /* Flatten takes care of lists in lists in lists in ... */
 /* List has zero non-null items, length() already ignores null values*/
 length(a!flatten(ri!value)) = 0,

 /* Map */
 if(
 local!typeNum = 'type!{http://www.appian.com/ae/types/2009}Map',
 /* Has no keys at all or all values are null */
 or(
 length(a!keys(ri!value)) = 0,
 all(a!isNullOrEmpty(_), index(ri!value, a!keys(ri!value), null))
 ),

 /* DataSubsets or Maps returned by queryRecordType */
 if(
 or(
 local!typeNum = 'type!{http://www.appian.com/ae/types/2009}DataSubset',
 and(
 local!typeNum = 'type!{http://www.appian.com/ae/types/2009}Map',
 contains(a!keys(ri!value), "data"),
 )
 ),
 a!isNullOrEmpty(ri!value.data),

 /* No idea what this could be so it is considered to not be null */
 false
 )
 )
 )
 )
 )
 )
)