:- use_module(library(terms)).(can be autoloaded)
?- A = a(1,2,3), term_size(A,S). S = 4. ?- A = a(1,2,3), term_size(a(A,A),S). S = 7. ?- term_size(a(a(1,2,3), a(1,2,3)), S). S = 11.
Note that small objects such as atoms and small integers have a size 0. Space is allocated for floats, large integers, strings and compound terms.