prolog-electric-dash-flag

prolog-electric-dash-flag is a variable defined in `prolog.el'.
Its value is

nil

Documentation:
Makes `-' electric (inserts a `-->' on a new line).
If non-nil, pressing `-' at the end of a line that starts in
the first column (i.e., DCG heads) inserts ` -->' and newline.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 24.1 of Emacs.