ListChanges ( oldList ; newList )

Returns

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Bruce Robertson - Show more from this author

Sample input:

ListChanges(
"1¶2¶3";
"A¶2¶B"
)

Sample output:

1 => A
3 => B

Function definition: (Copy & paste into FileMaker's Edit Custom Function window)

/*
ListChanges ( oldList ; newList )

walks lists
when they are not equal, returns in format
  oldValue => newValue
useful for recording record mods
Lists must be equal length.
You must escape any returns within
each item of the list

Bruce Robertson/Concise Design 
Last modified 2/22/2009
*/

Let([
N1 = ValueCount( oldList ) ;
N2 = ValueCount( newList );
A1 = GetValue( oldList; 1) ;
B1 = GetValue( newList; 1) ] ;

Case( 
N1 = 0 ; "" ;
N2 = 0 ; "" ;
N1 <> N2 ; "ERROR - list lengths do not match";

Case( A1 <> B1;
 A1 & " => " &  B1 & ¶ )  &
Case( N1 > 1;
ListChanges( 
RightValues ( oldList; N1-1 ); 
RightValues ( newList; N1-1 ) 
))
))

Compare two lists of equal length and return the changes in "oldvalue => newValue" format.

Useful for record change logs, for instance, when combined with on record load script and on record commit script. Use other custom functions or scripts to retrieve initial value on record open and final value on record submit.

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Note: these functions are not guaranteed or supported by BrianDunning.com. Please contact the individual developer with any questions or problems.

ListChanges ( oldList ; newList )

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