list.addRemove.fmfn

/*
 * list.addRemove ( value; valuelist )
 * RETURNS:  ( string ) The supplied list with the value either removed or concatenated 
 *
 */

Let ( [ //------------------------- VARIABLES
 
	var.list = Substitute ( If ( Left ( valuelist; 1 ) ≠ ¶; "^") & valuelist & "^"; ¶; "^^" ); // List minus all returns
	var.match = "^" & value & "^"; // Value to match
	var.exists = PatternCount ( var.list; var.match )

];  //------------------------- RESULT

	Case ( 
		var.exists;
			Let ( [
				var.removed = Substitute ( var.list; var.match; "" ); // Kill matching values
				var.list = Substitute ( var.removed; "^^"; ¶ ); // Put returns back in
				var.list = Middle ( var.list; 2; 100000 ); // Trim leading ^
				var.list = Left ( var.list; Length ( var.list ) - 1 ); // Trim trailing ^
				var.cleaned = Substitute ( var.list; ¶; "" ); // Remove returns for trimming
				var.char.first = Position ( var.list; Left ( var.cleaned; 1 ); 0; 1 ); // Position of firt non cleaned char
				var.char.last = Position ( var.list; Right ( var.cleaned; 1 ); Length ( var.list ); -1 ) // Position of last non cleaned char
			];
				Middle ( var.list; var.char.first; var.char.last - var.char.first + 1 )
			);

		If ( valuelist ≠ ""; valuelist & ¶ ) & value // default
	)

)

/*
 * Unit tests
 */
 
/*
Let (
_ = "--------------------";

 List (
  List ( "At beginning ( one )"; _; list.addRemove ( "one"; List ( "one"; "two"; "three" ) ); _ );
  List ( "At ending ( three )"; _; list.addRemove ( "three"; List ( "one"; "two"; "three" ) ); _ );
  List ( "With multiple spread out ( one )"; _; list.addRemove ( "one"; List ( "one"; "two"; "one"; "three" ) ); _ );
  List ( "With multiple at beginning ( one )"; _; list.addRemove ( "one"; List ( "one"; "one"; "two"; "three" ) ); _ );
  List ( "With multiple at ending ( three )"; _; list.addRemove ( "three"; List ( "one"; "two"; "three"; "three" ) ); _ );
  List ( "With multiple in middle ( two )"; _; list.addRemove ( "two"; List ( "one"; "two"; "two"; "three" ) ); _ );
  List ( "With even returns at start ( two )"; _; list.addRemove ( "two"; "¶¶¶¶one¶two¶three" ); _ );
  List ( "With odd returns at start ( two )"; _; list.addRemove ( "two"; "¶¶¶one¶two¶three" ); _ );
  List ( "With even returns at end ( two )"; _; list.addRemove ( "two"; "one¶two¶three¶¶¶¶" ); _ );
  List ( "With odd returns at end ( two )"; _; list.addRemove ( "two"; "one¶two¶three¶¶¶" ); _ );
  List ( "Without value ( one )"; _; list.addRemove ( "one"; List ( "two"; "three" ) ); _ );
  )
)
*/