worked example: active-logic

    description:
        proof of concept using simple if-then machines
        in this case, concerning wet grass, the sprinkler and rain

    code:
        -- learn the meaning of not:
        not |no> => |yes>
        not |yes> => |no>
        not |don't know> => |don't know>

        -- define our if-then machines:
        pattern |node 1: 1> => |grass is wet> + |not rained last night>
        then |node 1: 1> => 2.0|sprinkler was on> + -1.0|rained last night> + -1.0|not grass is wet>

        pattern |node 2: 1> => |grass is wet> + |not sprinkler was on>
        then |node 2: 1> => 2.0|rained last night> + -1.0|sprinkler was on> + -1.0|not grass is wet>

        pattern |node 3: 1> => |sprinkler was on>
        then |node 3: 1> => |grass is wet> + -1.0|not sprinkler was on>

        pattern |node 3: 2> => |rained last night>
        then |node 3: 2> => |grass is wet> + -1.0|not rained last night>

        pattern |node 4: 1> => |not rained last night> + |not sprinkler was on>
        then |node 4: 1> => 2.0|not grass is wet> + -1.0|rained last night> + -1.0|sprinkler was on>


        -- learn state of activation:
        active |rained last night> => |don't know>
        active |not rained last night> #=> not active |rained last night>
        active |sprinkler was on> => |don't know>
        active |not sprinkler was on> #=> not active |sprinkler was on>
        active |grass is wet> => |don't know>
        active |not grass is wet> #=> not active |grass is wet>


        -- activation states we want to unlearn:
        the-unlearn |list> => |rained last night> + |sprinkler was on> + |grass is wet>


        -- unlearn operators:
        unlearn |*> #=> learn(|op: active>, |_self>, |don't know>)
        unlearn-everything |*> #=> unlearn the-unlearn |list>


        -- our 'active' operators:
        make-active |*> #=> learn(|op: active>, remove-prefix["not "] |_self>, not has-prefix["not "] |_self>)
        currently-active |*> #=> such-that[active] rel-kets[active] |>
        read-sentence |*> #=> make-active words-to-list |_self>


        -- define our conclude operators:
        conclude |*> #=> drop then similar-input[pattern] such-that[active] rel-kets[active] |>
        inverse-conclude |*> #=> pattern similar-input[then] such-that[active] rel-kets[active] |>


        -- define short-cuts for our tables:
        t |*> #=> table[state, unlearn-everything, read-sentence, currently-active, conclude, inverse-conclude] the-list-of |states>
        t2 |*> #=> table[state, unlearn-everything, read-sentence, currently-active, conclude] the-list-of |states>


        -- learn the list of states we want in our tables:
        the-list-of |states> => |grass is wet>
        the-list-of |states> +=> |sprinkler was on>
        the-list-of |states> +=> |rained last night>
        the-list-of |states> +=> |sprinkler was on and rained last night>
        the-list-of |states> +=> |grass is wet and not rained last night>
        the-list-of |states> +=> |grass is wet and not sprinkler was on>
        the-list-of |states> +=> |not rained last night>
        the-list-of |states> +=> |not sprinkler was on>
        the-list-of |states> +=> |not rained last night and not sprinkler was on>
        the-list-of |states> +=> |not grass is wet>

    examples:
        unlearn-everything
            3|don't know>

        read-sentence |grass is wet and not rained last night>
            |yes> + |no>

        currently-active
            |not rained last night> + |grass is wet>

        conclude
            |sprinkler was on>


        t2
            +------------------------------------------------+--------------------+---------------+---------------------------------------------+-----------------------------------------------+
            | state                                          | unlearn-everything | read-sentence | currently-active                            | conclude                                      |
            +------------------------------------------------+--------------------+---------------+---------------------------------------------+-----------------------------------------------+
            | grass is wet                                   | 3 don't know       | yes           | grass is wet                                | 0.50 sprinkler was on, 0.50 rained last night |
            | sprinkler was on                               | 3 don't know       | yes           | sprinkler was on                            | grass is wet                                  |
            | rained last night                              | 3 don't know       | yes           | rained last night                           | grass is wet                                  |
            | sprinkler was on and rained last night         | 3 don't know       | 2 yes         | rained last night, sprinkler was on         | grass is wet                                  |
            | grass is wet and not rained last night         | 3 don't know       | yes, no       | not rained last night, grass is wet         | sprinkler was on                              |
            | grass is wet and not sprinkler was on          | 3 don't know       | yes, no       | not sprinkler was on, grass is wet          | rained last night                             |
            | not rained last night                          | 3 don't know       | no            | not rained last night                       | 0.50 sprinkler was on, 0.50 not grass is wet  |
            | not sprinkler was on                           | 3 don't know       | no            | not sprinkler was on                        | 0.50 rained last night, 0.50 not grass is wet |
            | not rained last night and not sprinkler was on | 3 don't know       | 2 no          | not rained last night, not sprinkler was on | not grass is wet                              |
            | not grass is wet                               | 3 don't know       | no            | not grass is wet                            |                                               |
            +------------------------------------------------+--------------------+---------------+---------------------------------------------+-----------------------------------------------+

    source code:
        load improved-active-logic.sw