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Fix readme file typos and code formatting issues #1

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Oct 28, 2019
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Fix readme file typos and code formatting issues #1

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28 changes: 15 additions & 13 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -16,7 +16,7 @@ In this library a situation is a list of fluents that hold in that state.
This list is what is passed around your application.

To change this list, you *should* only do so through actions, which
extend the action class:
extend the action prototype:

```logtalk
:- object(drop(_Item_),
Expand All @@ -25,15 +25,16 @@ extend the action class:
poss(Situation) :-
holding(_Item_)::holds(Situation).

retracts_fluents([holding(_Item_)]).
asserts_fluents([]).
retracts_fluents([holding(_Item_)]).

asserts_fluents([]).

:- end_object.
```

This describes a drop action that is only possible when holding the
item. All actions must have possible conditions, even if they're just
always possible: `poss(_).`
item. All actions must have possible conditions, even if they're
always possible by defining the predicate `poss/1` as `poss(_).`

An action is done like so:

Expand All @@ -42,7 +43,7 @@ An action is done like so:
?- Sit = [holding(ball)], drop(ball)::do(Sit, NextSit).
```

The values that change in the application are called fluents (because
The values that change in the application are called *fluents* (because
of the situation calculus influence). We need to define in what situations they
hold with what values. Most of the time, this will just be if that
fluent is a member of the situation list. In these cases you only need
Expand All @@ -52,6 +53,7 @@ their functors.
```logtalk
:- object(holding(_Item_),
extends(fluent)).

:- end_object.
```

Expand All @@ -61,10 +63,10 @@ Should the fluent be derived from others, this can be declared like so:
:- object(net_profit(_Profit_),
extends(fluent)).

holds(S) :-
gross_profit(P)::holds(S),
total_costs(C)::holds(S),
_Profit_ is P - C.
holds(S) :-
gross_profit(P)::holds(S),
total_costs(C)::holds(S),
_Profit_ is P - C.

:- end_object.
```
Expand Down Expand Up @@ -104,13 +106,13 @@ for actions:
:- object(boil_kettle,
extends(action)).

poss(S) :-
situation::holds(power(kettle, on) and not kettle_water(empty), S).
poss(S) :-
situation::holds(power(kettle, on) and not kettle_water(empty), S).

:- end_object.
```

As we're in Prolog, `not` has the same meaning as `\+`.
As we're in Logtalk, `not/1` has the same meaning as `\+/1`.

Finally, to persist a situation between sessions, persist the list of
fluents and reload. This method of state handling clobbers it's history
Expand Down