These functions write to the standard output file, typically the screen. The princ and pretty_princ functions produce formatted output, which means that special characters are not escaped, and double quotes are not printed around character strings. Output generated by princ cannot be read by the Lisp reader.
print and pretty_print produce Lisp-readable output. The result of reading a printed expression using a call to read will generate an equal expression.
pretty_princ and pretty_print generate carriage returns and spaces with the intention of formatting the output to make long or complex Lisp expressions easier for a person to read.
Gamma> x = "hello";
"hello"
Gamma> print (x,"\n");
"hello""\n"t
Gamma> princ (x,"\n");
hello
t
Gamma> >
Gamma> class C {a; b; c;}
(defclass C nil [][a b c])
Gamma> princ (C);
(defclass C nil [][a b c])t
Gamma> pretty_princ (C);
(defclass C nil
[]
[a b c])t
Gamma>
Gamma> L = list (1,2,3,4,5,list(1,2,3,4,5,list(1,2,3
list(1,2,3,4,5,list(1,2,3,4,5,list(1,2,3,4,5,list(1,2
,list(1,2,3,4,5,list(1,2,3,4,5)))))))))));
(1 2 3 4 5 (1 2 3 4 5 (1 2 3 4 5 (1 2 3 4 5 (1 2 3 4
4 5 (1 2 3 4 5 (1 2 3 4 5 (1 2 3 4 5 (1 2 3 4 5)))))
Gamma> princ (L);
(1 2 3 4 5 (1 2 3 4 5 (1 2 3 4 5 (1 2 3 4 5 (1 2 3 4
4 5 (1 2 3 4 5 (1 2 3 4 5 (1 2 3 4 5 (1 2 3 4 5)))))
Gamma> pretty_princ (L);
(1 2 3 4 5
(1 2 3 4 5
(1 2 3 4 5
(1 2 3 4 5
(1 2 3 4 5
(1 2 3 4 5
(1 2 3 4 5 (1 2 3 4 5 (1 2 3 4 5 (
))))))))))t
Gamma>
See the Starting Programs section of the Common Functions chapter (Tutorial One) in the Cogent Tools Demo and Tutorials book for an example of this function used in context.