So, I am working on my Senses System (see my journal) and I temporarily typed the following code(LUA):

function TriggerEmotionChange()
    if See(box) then
        mood = 10
        setText(state, getName(box) .. "es " .. "make me glad")
    elseif See(monkey) then
        mood = 3
        setText(state, getName(monkey) .. "s " .. "make me sad")
    elseif See(building) then
        mood = 5
        setText(state, getName(building) .. "s " .. "make me turn around in circles")
    end
end

This made me want to create a grammar system. I know I need to do some operations on strings, namely checking whether the last letter in a string is a certain letter and then adding the appropriate ending. I know I would do a few if/else statements and then one else statement to check if all other letters of the alphabet.

Just in case someone wanted to know what the code does:

In the example above, the getName() function gets the name of the game object and returns a string.

The "state" variable is just a text game object.

The value of the mood value determines the emotional state of the character.

Anyone have any tips on how I might go about the grammar system (shouldn't take long to implement it) for "ing" and "es or s" endings?

Just a little something to get me started on how I should approach it in an efficient way?

Are you interested in creating your grammar rules in Lua, or can it be in C++? If the latter, then why not just use an existing parser generator like Boost::Spirit? Then you can have true support for your own domain specific language without doing the low level string manipulations.

What you need is a lexicon with words and what their other form(s) are.

^ That is how I would do it.

For any string that you want to do this to you could store its singular and plural forms (e.g. monkey stores its name in singular and plural form). Then you can just call getNamePluralised(monkey) to return the plural form.

Some examples:

(box, boxes)

(monkey, monkeys)

(building, buildings)

(sheep, sheep)

(ability, abilities)

(bacterium, bacteria)

(cactus, cacti)

Clearly no amount of "ing", "es, "s" manipulation is going to take you from cactus to cacti.

Hmm, good responses. It looks like I could use a table that stores all endings and somehow go from there. I'll try to figure this out ASAP so I can post the results on this same topic, in case someone else later comes along and wants to do the same thing.

I could have the See() function take two arguments, one would be the object being seen, and the latter could be the ending:

See(box,es)

Look(boy,s)

Start(walk,ing)

Indeed going from cactus to cacti would not work in this case. This could be revised somehow. I could do the base of the word like:

See(cact,us)
See(cact,i)

Then I could check the ending and run either a single collision test or test multiple collisions (see multiple things).

function Smell(object,ending)
    if isCollisionBetween(Player,object) then
        setText(txt_smelling, "I smell " .. getName(object) .. ending)
    end
end
    

In this case if I did:

Smell(box)

If I wanted it singular, I would have to have an "a" in there for "I smell a box."

Plural would be:

Smell(box,"es")

I can do a conditional statement based on the ending, but I don't know how I would change to the singular unless I do a conditional statement somewhere (don't know how it would look yet).

Seems I could set all endings explicitly first as variables:

s = "s"
es = "es"
ing = "ing"
us = "us"
i = "i"
-- gotta watch that one as "i" can be a counter too. But I could use "j" instead. 
 
ending = ing
 
print(ending)
--ing

I like the way that Django (Python web framework) handles plurals. When you create a database table, you create it as a Python class, e.g. "class Reply(models.Model)". When displaying the reply table contents on the admin site, it guesses the plural by just adding an -s (so "replys"), however you change this by overriding it like this:

class Reply(models.Model):
	class Meta:
		verbose_name_plural = "Replies"; 

Android handles this by using quantity strings in resource files; the documentation has a good example of how this works.

I think for your code, what would work best is a system similar to Django's (assume -s unless overriden). Here's an example of these:

-- Create a class called object
local Object = { };


-- Name is string; pluralName is string or nil
function Object.new(name, pluralName)
	name = tostring(name);
	-- If no plural name was provided, assume it's just add -s       random ' to fix highlighting
	pluralName = pluralName or name.."s";

	local object = { };

	object.name = name;
	object.pluralName = pluralName;

	-- Requires the metatable for the class system to work
	setmetatable(object, {__index = Object});
	return object;
end


-- Methods
function Object:getName()
	return self.name;
end



function Object:getPluralName()
	return self.pluralName;
end



-- Dummy methods for testing
local function isCollisionBetween(objectA, objectB)
	return true;
end



local textSmelling = "SMELLING";
local function setText(type, text)
	print(type, text);
end



-- Using it:
local Player = { };

function Player:smell(object)
	if (isCollisionBetween(self, object)) then
		setText(textSmelling, "I smell "..object:getPluralName());
	end
end



local apple = Object.new("apple");
local cactus = Object.new("cactus", "cacti");

Player:smell(apple);
Player:smell(cactus);

I tested it on the Lua online demo and got:

SMELLING	I smell apples
SMELLING	I smell cacti