Q:

How to deconstruct a compound term in SWI Prolog

I have compound terms that can have a  number inside the braces.
For example: qpowieipq(5),lsjdlasa(15) or lkjlk. I got it from the database (like my_list([rxclk,rxer,rxdv,rxd(0),rxd(1),rxd(2),crs,col,txen,txd(0),txd(1),txd(2),‌​txd(3)]).).
How can I get the value of the number inside the braces?
For example: 
my_function(qpowieipq(5), X).
X=5.
my_function(lsjdlasa(15), X).
X=15.
my_function(lkjlk, X).
false

I am using SWI Prolog.

A:

You can use (=..)/2 and pattern matching to deconstruct Prolog's compound terms. For instance
?- a =.. X.
X = [a].

?- a(1) =.. X.
X = [a, 1].

So, tentatively
my_function(T, V) :- T =.. [_,V], number(V).

This will work with any ISO compliant Prolog processor.

