The printf/2, 3 Predicate

  This predicate subsumes all other output predicates, and it also offers formatted printing. Its syntax is similar to the C printf(3) function, but it also has further Prolog-specific options. For example, the sequence

write('The result is '),
writeq(T),
write(', which is '),
write(P),
write('% better than '),
write(R),
nl,
flush(output).

printf("The result is %q, which is %d%% better than %w\n%b", [T, P, R]).

O

ignore operator declarations

D

disregard depth limit for nested terms

.

print lists as ./2 structures

Q

print quotes around functors when needed

v

print variables as unique numbers, e.g. _g123

V

print variables as names and numbers, e.g. X_g123

P

use portray/1,2 if defined

U

use portray/1,2 even for variables

m

print metaterm attributes using user-defined handlers

M

print metaterm attributes in a standard form

G

print term as a goal, i.e. apply goal write macros

T

don't apply write macro transformations

write(X)           :- printf("%w",    [X]).
writeq(X)          :- printf("%QDTMvw", [X]).
print(X)           :- printf("%Pw",   [X]).
display(X)         :- printf("%O.w",  [X]).
write_canonical(X) :- printf("%O.QDTMvw", [X]).