The fl BASIC program forms a single list from two lists using intersection, union, or exclusion operators.
fl file.reference1 list1{operators} {file.reference2} {list2}
fl ?
| list1 | First list. | |
| list2 | Second list. | |
| operators | = | Indicates an intersection. Forms list of matching items. |
| + | Indicates a union. Forms list of nonduplicate items. | |
| - | Indicates an exclusion. Forms list of items not in list2. | |
| ? | Displays help text on the screen. | |
If file.reference2 is not specified, it is assumed to be the same as file.reference1. If list2 is not specified, it is assumed to be the same as list1. If neither file.reference2 nor list 2 are specified, the effect is the same as a get-list. The created list overlays list1 in file.reference1.
Example 1
Creates a list of all sports fans from both lists:
fl pointer-file football.fans + baseball.fans
Example 2
Creates a list of those who enjoy both sports:
fl pointer-file football.fans = baseball.fans
Example 3
Creates a list of those who like football only:
fl pointer-file football.fans - baseball.fans