How to make simple programming language in Hollywood?

[Bugala]

Since im not sure how to make the actual question, I am going to first explain what i have been doing.

I have in couple of my projects made engine that is controlled by simple programming language kind of thing that uses tables for its execution. An example table could be:

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attackwave = {
                [1] = {type=enemy, numberofenemies=2,
                       [1] = {x=100, y=200, type=3},
                       [2] = {x=300, y=200, type=1}
                        },
                 [2] = {type=displaytext, text="Incoming attack!"},
                 [3] = {type=enemy, numberofenemies=1,
                     [1] = {x=300, y=100, type=2}
                         }
                     }

Idea is that the execution would go one table index at a time. That for example in this case engine would handle that first there would come two enemies with given specifics, and after those both have been shot there would be text displayed on screen, and after displaying text have been done, the next attackwave would start.

So far this have worked somewhat okay for me, but lately my engines have become bit more complex and this is starting to show its limits.

As example I many times use program flow commands like "jump" command which i use to jump to some specific place in table (like jumping to specifil line of code) it could be for example "jump=1" which would mean that it would jump to first index of table.

Two examples about how this jump command is starting to be bit of a problem to me:

1. I can use jump=1 to jump to table[1], but what if i want to jump say, table[1][1]? Then i would need to make another command like subjump and if i want to jump to table[1][1][1], i need a third command.

2. More serious problem is that when I use program to jump to some specific place in middle of code. Say with answer 1 jump=10, ith answer 2 jump=23. So far so good, but then i decide to add more lines between lines 10 and 23, this means that i need to go back this jump=23 place, and change it accordingly.

And especially if there are more than just one jump on same piece of table code and i go on to add one line to one of the first lines, then i need to change all the jump=x lines.


So now we get to the actual question.

I have been thinking for some time now, that i need some better system for my engine codes than using tables.

I would like to rather use some written code, like hollywood does. But problem is that I dont quite get how that is done.

So how for example if I would have textfile like:

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Wave1:
Createenemy(1, 200, 300, 50)" 
Goto Wave1:

(makes enemy of type 1 to location x200 y300 with 50 units of health)

How would I be able to read that in hollywood so I could use that info?

That how do i make hollywood understand that for example Createenemy is the command and first number inside () is enemy type, next number is x...
and how would i tell hollywood to for example find the location wave1:?

Could someone please give me some example code about this, for I dont have much clue about how this is done in practice.

All I can think about is checking everything letter by letter and comparing them to commands but that doesnt seem very practical way to do it.

[jalih]

Idea is that the execution would go one table index at a time. That for example in this case engine would handle that first there would come two enemies with given specifics, and after those both have been shot there would be text displayed on screen, and after displaying text have been done, the next attackwave would start.

So far this have worked somewhat okay for me, but lately my engines have become bit more complex and this is starting to show its limits.

In my system you can register different game states by names. Each game state can have: "init", "draw" and "update" events. These events are issued at the user controlled frame rate, if system is fast enough to handle it. Delta timing and finer control for handling the drawing event is supported, so you can skip frames if system is not fast enough.

In your example case, you could create:

- "NextAttackWave" state to handle initialization of the alien attack wave
- "GetReady" state to handle displaying the "Incoming attack" text on screen.
- Use default "main" state to handle the actual game loop.


If you really are interested about writing your own programming language then grab Compiler Construction - N. Wirth. Study the material and start by writing some scanners and parsers first.