-.. raw:: latex
-
- \newpage
-
=================
Heidi revisited
=================
.. epigraph::
- | *I was an innkeeper, who loved to carouse;*
- | *J was a joiner, and built up a house.*
+ | |CENTER| *I was an innkeeper, who loved to carouse;*
+ | |CENTER| *J was a joiner, and built up a house.*
.. only:: html
.. image:: /images/picI.png
:align: left
-.. raw:: latex
-
- \dropcap{i}
-
-n even the simplest story, there's bound to be scope for the player to
+|I|\n even the simplest story, there's bound to be scope for the player to
attempt activities that you hadn't anticipated. Sometimes there may be
alternative ways of approaching a problem: if you can't be sure which
approach the player will take, you really ought to allow for all
need to substitute a more relevant response after LISTEN TO BIRD. Here's
how we do it:
-.. code-block:: inform6
+.. code-block:: inform
Object bird "baby bird" forest
with description "Too young to fly, the nestling tweets helplessly.",
though it hadn't been intercepted. Sometimes that's what you want it to
do, but not here: if instead we'd written this:
-.. code-block:: inform6
+.. code-block:: inform
Object bird "baby bird" forest
with description "Too young to fly, the nestling tweets helplessly.",
Again, that isn't perhaps the most appropriate response, but it's easy to
change:
-.. code-block:: inform6
+.. code-block:: inform
Object before_cottage "In front of a cottage"
with description
That's easy to fix; we can add a new ``cottage`` object, making it a piece
of ``scenery`` just like the ``tree``:
-.. code-block:: inform6
+.. code-block:: inform
Object cottage "tiny cottage" before_cottage
with description "It's small and simple, but you're very happy here.",
The situation here is similar to our LISTEN TO BIRD problem, and the
solution we adopt is similar as well:
-.. code-block:: inform6
+.. code-block:: inform
Object cottage "tiny cottage" before_cottage
with description "It's small and simple, but you're very happy here.",
turns out that the sequence "``print`` a string which ends with a newline
character, and then ``return true``" is so frequently needed that there's a
special statement which does it all. That is, this single statement (where
-you'll note that the string doesn't need to end in ``^``)::
+you'll note that the string *doesn't* need to end in ``^``)::
print_ret "It's such a lovely day -- much too nice to go inside.";
to be achieved by that"). Yet another opportunity to use a ``before``
property, but now with a difference.
-.. code-block:: inform6
+.. code-block:: inform
Object tree "tall sycamore tree" clearing
with description
object, it's not in order to display a better message; it's because we want
to move the player character to another room, just as if she'd typed UP.
Relocating the player character is actually quite a complex business, but
-fortunately all of that complexity is hidden: there's a standard **library
-routine** to do the job, not one that we've written, but one that's
-provided as part of the Inform system.
-
-You'll remember that, when we first mentioned routines (see "Standalone
-routines" on page 57), we used the example of ``Initialise()`` and said
-that "the routine's name followed by opening and closing parentheses is all
-that it takes to call a routine". That was true for ``Initialise()``, but
-not quite the whole story. To move the player character, we've got to
-specify where we want her to go, and we do that by supplying the internal
-ID of the destination room within the opening and closing parentheses.
-That is, instead of just ``PlayerTo()`` we call ``PlayerTo(top_of_tree)``,
-and we describe ``top_of_tree`` as the routine's **argument**.
+fortunately all of that complexity is hidden: there's a standard
+:term:`library routine` to do the job, not one that we've written, but one
+that's provided as part of the Inform system.
+
+You'll remember that, when we first mentioned routines (see
+:ref:`standalone-routines`), we used the example of ``Initialise()`` and
+said that "the routine's name followed by opening and closing parentheses
+is all that it takes to call a routine". That was true for
+``Initialise()``, but not quite the whole story. To move the player
+character, we've got to specify where we want her to go, and we do that by
+supplying the internal ID of the destination room within the opening and
+closing parentheses. That is, instead of just ``PlayerTo()`` we call
+``PlayerTo(top_of_tree)``, and we describe ``top_of_tree`` as the routine's
+:term:`argument`.
Although we've moved the player character to another room, we're still in
the middle of the intercepted ``Climb`` action. As previously, we need to
far, but instead for every ``Drop`` which takes place in our troublesome
``top_of_tree`` room. This is what we have to write:
-.. code-block:: inform6
+.. code-block:: inform
Object top_of_tree "At the top of the tree"
with description "You cling precariously to the trunk.",
unhelpful in these non-standard circumstances. If you prefer to hint at
what's just happened, you could use this alternative solution:
-.. code-block:: inform6
+.. code-block:: inform
Object top_of_tree "At the top of the tree"
with description "You cling precariously to the trunk.",
checked for the bird actually being in the nest; fortunately, that's easy
to do:
-.. code-block:: inform6
+.. code-block:: inform
Object branch "wide firm bough" top_of_tree
with description "It's flat enough to support a small object.",
if (bird in nest && nest in branch) deadflag = 2;
should now be read as: "Test whether the ``bird`` is currently in (or on)
-the ``nest``, and whether the ``nest`` is currently on (or in) the
+the ``nest``, *and* whether the ``nest`` is currently on (or in) the
``branch``; if both parts are ``true``, set the value of ``deadflag`` to 2;
otherwise, do nothing".
The new topics that we've encountered here include these:
-.. rubric:: Object properties
+Object properties
+-----------------
Objects can have a ``before`` property -- if there is one, the interpreter
looks at it *before* performing an action which in some way involves that
in_to "It's such a lovely day -- much too nice to go inside.",
cant_go "The only path lies to the east.",
-.. rubric:: Routines and arguments
+.. _routines-args:
+
+Routines and arguments
+----------------------
The library includes a number of useful routines, available to perform
-certain common tasks if you require them; there's a list in "Library
-routines" on page 264. We used the ``PlayerTo`` routine, which moves the
+certain common tasks if you require them; there's a list in
+:ref:`library-routines`. We used the ``PlayerTo`` routine, which moves the
player character from her current room to another one -- not necessarily
adjacent to the first room.
PlayerTo(clearing);
-A value given in parentheses like that is called an **argument** of the
+A value given in parentheses like that is called an :term:`argument` of the
routine. In fact, a routine can have more than one argument; if so,
they're separated by commas. For example, to move the player character to
a room *without* displaying that room's description, we could have supplied
In this example, the effect of the ``1`` is to prevent the description
being displayed.
-.. rubric:: Statements
+Statements
+----------
We encountered several new statements:
The value ``nothing`` is a built-in constant (like ``true`` and ``false``)
which means, well, there isn't any object to refer to. There's a list of
-standard library actions in "Group 1 actions" on page 270, "Group 2
-actions" on page 271 and "Group 3 actions" on page 271.
+standard library actions in :ref:`group-1-actions`, :ref:`group-2-actions`
+and :ref:`group-3-actions`.
We've now reached the end of our first game. In these three chapters we've
shown you the basic principles on which almost all games are based, and
introduced you to many of the components that you'll need when creating
more interesting IF. We suggest that you take one last look at the source
-code (see "Heidi" story on page 213), and then move on to the next stage.
+code (see :doc:`/appendices/b`), and then move on to the next stage.
projects / ibg.git / blobdiff