A file pointer to a previously opened file. This may be either a file in the file system, or a string opened for read and write.
This function reads from the current location in the file to the end, evaluating its contents as Lisp expressions and counting them.
The file "myevalfile.dat" contains the following:
(+ 3 4) 3 + 2;
Gamma> ft = open ("myevalfile.dat", "r");
#<File:"myevalfile.dat">
Gamma> read_eval_file(ft);
4
Gamma> close(ft);
t
Gamma>