Would somebody please explain the said lines in this test?

[peerreynders]

@pillaiindu

I think you wanted to say "Any = inside Pattern (i.e., [p1 = %Product{}, p2 = %Product{}] in this case) is just a binding pattern match, not pattern match binding.

With regards to [p1 = %Product{}, p2 = %Product{}]

• the pattern match is essentially [%Product{}, %Product{}] = Catalog.list_products i.e. a two element list where each element has to be a Product structure - otherwise the match will fail.
• after the match is successful the names p1 and p2 are bound to their values. p1 is bound to the first element in the list and p2 is bound to the second element in the list.

Now consider [p1, p2] = Catalog.list_products:

• the pattern match is essentially [_, _] = Catalog.list_products i.e. a two element list where each element can be any data type - otherwise the match will fail.
• after the match is successful the names p1 and p2 are bound to their values. p1 is bound to the first element in the list and p2 is bound to the second element in the list.

Finally [^p1, ^p2] = Catalog.list_products

• The match will only succeed if the first element of the list matches the current content of p1 and the second element matches the current content of p2 (and the list has exactly two elements).

@rvirding

So a classic variable is basically a hole and the name is a reference to that hole so so reassigning a variable fills the hole with a new value which will be seen by everyone. A functional variable is just a reference to data.