Type tests are semi-deterministic predicates that succeed if the
argument satisfies the requested type. Type-test predicates have no
error condition and do not instantiate their argument. See also library
library(error)
.
"hello"
creates a list of character
codes. We illustrate the issues in the example queries below.
?- write("hello"). [104, 101, 108, 108, 111] true. ?- string("hello"). false. ?- is_list("hello"). true.