25.2.10  Difference between operators := and =<

The := and =< assignment operators have different effects when they are used to modify an element of a list contained in a variable, since =< modifies the element by reference. Otherwise, they will have the same effect.

Example

Now

and

both change A[1] to 5:

but they do it in different ways. The command A[1]=<5 changes the middle value in the list that A originally pointed to, and so any other variable pointing to the list will be changed, but A[1]:=5 will create a duplicate list with the middle element of 5, and so any other variable pointing to the original list won’t be affected.

Examples

If B is set equal to a copy of A instead of A, then changing B won’t affect A.