From def04721be506f1c7ff5ddf407f2333999570a89 Mon Sep 17 00:00:00 2001
From: Mark Green <mark@antelope.nildram.co.uk>
Date: Fri, 22 Jan 2016 00:54:44 +0000
Subject: Add a try at an Inform 7 tutorial.
Obscure, but really interesting.
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+---
+language: Inform7
+contributors:
+ - ["Hyphz", "http://github.com/hyphz/"]
+filename: LearnInform.Inform
+---
+Inform 7 is a natural language based language created by Graham Nelson and Emily Short for writing text adventures, but also potentially usable for other text based applications, especially data backed ones.
+
+```
+"LearnInform" by Hyphz
+
+[This is a comment.]
+
+[Inform 7 is a language designed for building text adventures.
+It can be used for other purposes too, although the default
+library builds a text adventure. Inform 7 is object oriented.]
+
+[This creates a class by subclassing. "Value" is the universal subclass,
+but "object" is the most basic that behaves like an OO object.]
+A datablock is a kind of object.
+
+[Classes can have properties.]
+A datablock can be broken. [This creates a boolean property.]
+A datablock is usually not broken. [This sets its default value.]
+A datablock can be big or small. [This creates an enumerated property.]
+A datablock is usually small. [This sets its default value.]
+A datablock has a number called the sequence number. [This creates a typed property.]
+A datablock has some text called the name. ["Some text" means a string.]
+A datablock has a datablock called the chain. [Declared classes become types.]
+
+[This creates a global named instance.]
+Block1 is a datablock.
+The sequence number of Block1 is 1.
+The name of Block1 is "Block One."
+
+[Functions and procedures are defined as "phrases".]
+To do the thing everyone does with their first program:
+ say "Hello World.". [Full stop indicates the end, indent indicates the scope.]
+
+To dump (the block - a datablock): [That's how we create a parameter.]
+ say the sequence number of the block;
+ say the name of the block;
+ if the block is broken, say "(Broken)".
+
+To toggle (the block - a datablock):
+ if the block is broken: [Conditional.]
+ now the block is not broken; [Updating a property.]
+ else:
+ now the block is broken.
+
+[Multiple parameters.]
+To fix (the broken block - a datablock) using (the repair block - a datablock):
+ if the broken block is not broken, stop; [Comma for a non indented single command.]
+ if the repair block is broken, stop;
+ now the sequence number of the broken block is the sequence number of the repair block;
+ now the broken block is not broken.
+
+[Because of its text adventure origins, Inform 7 doesn't generally allow objects
+to be created dynamically, although there's a language extension that enables it.]
+Block2 is a datablock.
+Block2 is broken.
+The sequence number of Block2 is 2.
+The name of Block2 is "Block two."
+
+To demonstrate calling a phrase with two parameters:
+ Let the second block be block2; [Local pointer variable.]
+ fix the second block using Block1;
+ say the sequence number of the second block. [1.]
+
+[Lists.]
+To show how to use list types:
+ let the list be a list of datablocks;
+ add Block1 to the list;
+ add Block2 to the list;
+ say the list; ["Block1 and Block2"]
+ [Membership.]
+ if Block1 is listed in the list:
+ say "Block1 is there.";
+ [Loop.]
+ repeat with the block running through the list:
+ dump the block; [1 Block One. 1 Block Two.]
+ [Remember block two's sequence number was changed above.]
+ let X be entry 2 of the list; [Counting starts at 1.]
+ dump X; ["1 Block two."]
+ remove X from the list;
+ say the list. [Block1]
+
+[Here's how we define a function and do arithmetic.]
+
+To decide which number is the sum of all numbers up to (X - a number) (this is summing up):
+ let the total so far be a number;
+ repeat with the current number running from 1 to X:
+ now the total so far is the total so far + the current number;
+ decide on the total so far. [This is the return statement.]
+
+[ We have higher order functions too. ]
+
+To demonstrate a higher order function:
+ say summing up applied to {1, 2, 3, 4}.
+
+To decide which number is the result of applying (phrase - phrase A -> A) twice to (B - a value of kind A):
+ let b1 be phrase applied to B;
+ let b2 be phrase applied to b1;
+ decide on b2.
+
+To demonstrate defining a higher order function:
+ let X be 5;
+ say the result of applying summing up twice to X.
+
+[ Rulebooks allow a number of functions which apply to the same type under different conditions to be stacked. ]
+
+Datablock validation rules is a datablock based rulebook.
+
+A datablock validation rule for a broken datablock: rule fails.
+A datablock validation rule for a datablock (called the block):
+ dump the block;
+ rule succeeds.
+
+To demonstrate invoking a rulebook:
+ follow datablock validation rules for Block1;
+ follow datablock validation rules for Block2.
+
+[ Objects can also have relations, which resemble those in a relational database. ]
+A dog is a kind of thing.
+Rover is a dog.
+The kennel is a container. [This is a built in base class.]
+Rover is in the kennel. [This creates an inbuilt relation called "containment".]
+
+[We can create relations by declaring their type.]
+
+Guide dog ownership relates one dog to one person. [One-to-one.]
+Property ownership relates various things to one person. [Many-to-one.]
+Friendship relates various people to various people. [Many-to-many.]
+
+[To actually use them we must assign verbs or prepositions to them.]
+
+The verb to own means the property ownership relation.
+The verb to be the guide dog of means the guide dog ownership relation.
+The verb to be guided by means the reversed guide dog ownership relation.
+The verb to be friends with means the friendship relation.
+
+Edward is a person. A person can be blind. Edward is blind.
+Edward is guided by Rover.
+Benny is a person. Edward is friends with Benny.
+
+To demonstrate looking something up with a relation:
+ repeat with the dog running through things that are the guide dog of Edward:
+ say the dog;
+ repeat with the friend running through things that are friends with Edward:
+ say the friend.
+
+[We can also define relations that exist procedurally.]
+
+Helpfulness relates a person (called the helper) to a person (called the helpee) when the helpee is blind and the helper is not blind.
+The verb to be helpful to means the helpfulness relation.
+To demonstrate using a procedural relation:
+ repeat with the helper running through people that are helpful to Edward:
+ say the helper.
+
+
+[ Interface to the text adventure harness to allow the above code to be run. ]
+Tutorial room is a room.
+"A rather strange room full of buttons. Push them to run the exercises, or turn on the robot to run them all."
+A button is a kind of thing. A button is fixed in place.
+
+The red button is a button in tutorial room.
+Instead of pushing the red button, do the thing everyone does with their first program.
+The green button is a button in tutorial room.
+Instead of pushing the green button, demonstrate calling a phrase with two parameters.
+The blue button is a button in tutorial room.
+Instead of pushing the blue button, show how to use list types.
+The cyan button is a button in tutorial room.
+Instead of pushing the cyan button, say the sum of all numbers up to 5.
+The purple button is a button in tutorial room.
+Instead of pushing the purple button, demonstrate a higher order function.
+The black button is a button in tutorial room.
+Instead of pushing the black button, demonstrate defining a higher order function.
+The white button is a button in tutorial room.
+Instead of pushing the white button, demonstrate invoking a rulebook.
+The puce button is a button in tutorial room.
+Instead of pushing the puce button, demonstrate looking something up with a relation.
+The orange button is a button in tutorial room.
+Instead of pushing the orange button, demonstrate using a procedural relation.
+
+The robot is an object in tutorial room.
+Instead of switching on the robot:
+ say "The robot begins to frantically flail its arms about.";
+ repeat with button running through buttons in the tutorial room:
+ say "The robot randomly hits [the button].";
+ try pushing button.
+```
+
+##Ready For More?
+
+* [Inform 7](http://www.inform7.com/)
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