The command-line editor

The command-line editor resides at the top-level of the system, and accepts queries from user. A query is a Prolog goal that ends with a new line. It is a tradition that a period is used to terminate a query. In B-Prolog, since queries cannot expand over more than one line, the terminating period can be omitted.

The command-line editor accepts the following editing commands:

^F	Move the cursor one position forward.
^B	Move the cursor one position backward.
^A	Move the cursor to the beginning of the line.
^E	Move the cursor to the end of the line.
^D	Delete the character under the cursor.
^H	Delete the character to the left of the cursor.
^K	Delete the characters to the right of the cursor.
^U	Delete the whole line.
^P	Load the previous query in the buffer.
^N	Load the next query in the buffer.

Note that, as mentioned above, the command ^D will halt the system if the line is empty and the cursor is located at the beginning of the line.