Chapter 1

Intermediate LPC

Descartes of Borg

November 1993

CHAPTER 1: Introduction

1.1 LPC Basics

Anyone reading this textbook should either have read the textbook LPC Basics or be familiar enough with mud realm coding such that not only are they capable of building rooms and other such objects involved in area coding, but they also have a good idea of what is going on when the code they write is executing. If you do not feel you are at this point, then go back and read LPC Basics before continuing. If you do so, you will find that what you read here will be much more meaningful to you.

1.2 Goals of This Textbook

The introductory textbook was meant to take people new to LPC from knowing nothing to being able to code a nice realm on any LPMud. There is naturally much more to LPC and to LPMud building, however, than building rooms, armours, monsters, and weapons. As you get into more complicated concepts like guilds, or desire to do more involved things with your realm, you will find the concepts detailed in LPC Basics to be lacking in support for these projects. Intermediate LPC is designed to take you beyond the simple realm building process into a full knowledge of LPC for functioning as a realm builder on an LPMud. The task of mudlib building itself is left to a later text. After reading this textbook and working through it by experimenting with actual code, the reader should be able to code game objects to fit any design or idea they have in mind, so long as I have been successful.

1.3 An Overview

What more is there? Well many of you are quite aware that LPC supports mappings and arrays and have been asking me why those were not detailed in LPC Basics. I felt that those concepts were beyond the scope of what I was trying to do with that textbook and were more fitting to this textbook. But new tools are all fine and dandy, what matters, however, is what you can do with those tools. The goal of LPC Basics was to get you to building quality LPMud realms. Mappings and arrays are not necessary to do that. The goal of this book is to allow you to code any idea you might want to code in your area. That ability requires the knowledge of mappings and arrays.

Any idea you want to code in an LPMud is possible. LPC is a language which is amazingly well suited to this task. All that prevents you from coding your ideas is your knowledge of LPC or an inadequate mudlib or your mudÕs theme or administrative policies. This textbook cannot make the mudlib you are working with any better, and it cannot change the mud theme or the mudÕs administrative policies. Never once think that LPC is incapable of doing what you want to do. If your idea is prevented by administrative policies or themes, then it is simply not an idea for your current mud. If the mudlib is inadequate, talk to the people in charge of your mudlib about what can be done at the mudlib level to facilitate it. You would be surprised by what is actually in the mudlib you did not know about. More important, after reading this textbook, you should be able to read all of the mudlib code in your mudÕs mudlib and understand what is going on at each line in the mudlib code. You may not as yet be able to reproduce that code on your own, but at least you can understand what is going on at the mudlib level.

This textbook starts out with a discussion about what the LPMud driver is doing. One nice thing about this textbook, in general it is completely driver and mudlib independent (excepting for the Dworkin Game Driver). The chapter on the game driver does not get into actual implementation, but instead deals with what all game drivers basically do in order to run the mud.

Next I discuss those magic topics everyone wants to know more about, arrays and mappings. Mappings may be simultaneously the easiest and most difficult data type to understand. Since they are sort of complex arrays in a loose sense, you really need to understand arrays before discussing them. All the same, once you understand them, they are much easier than arrays to use in real situations. At any rate, spend most of your time working with that chapter, because it is probably the most difficult, yet most useful chapter in the book.

After that follows a brief chapter on the LPC pre-compiler, a tool you can use for sorting out how your code will look before it gets sent to the compiler. Despite my horrid intro to it here, this chapter is perhaps the easiest chapter in the textbook. I put it after the mappings and arrays chapter for exactly that reason.

Strings are re-introduced next, going into more detail with how you can do such things as advanced command handling by breaking up strings. Once you understand arrays fairly well, this chapter should be really simple.

The next chapter is the second most important in the book. It may be the most important if you ever intend to go beyond the intermediate stage and dive into mudlib coding. That chapter involves the complex ideas behind LPC inheritance. Since the goal of this textbook is not to teach mudlib programming, the chapter is not a detailed discussion on object oriented programming. Understanding this chapter, however, will give you some good insights into what is involved with object oriented programming, as well as allow you to build more complex objects by overriding functions and defining your own base classes.

Finally, the textbook ends with a simple discussion of code debugging. This is not an essential chapter, but instead it is meant as more of an auxiliary supplement to what the knowledge you have accumulated so far.

1.4 Not Appearing in This Textbook

Perhaps what might appear to some as the most glaring omission of this textbook is largely a political omission, shadows. Never have I ever encountered an example of where a shadow was either the best or most effecient manner of doing anything. It does not follow from that, however, that there are no uses for shadows. My reasoning for omitting shadows from this textbook is that the learner is best served by learning the concepts in this textbook first and having spent time with them before dealing with the subject of shadows. In that way, I feel the person learning LPC will be better capable of judging the merits of using a shadow down the road. I will discuss shadows in a future textbook.

If you are someone who uses shadows some or a lot, please do not take the above paragraph as a personal attack. There may be some perfectly valid uses for shadows somewhere which I have yet to encounter. Nevertheless, they are not the ideal way to accomplish any given task, and therefore they are not considered for the purposes of this textbook an intermediate coding tool.

I have also omitted discussions of security and object oriented programming. Both are quite obviously mudlib issues. Many people, however, might take exception with my leaving out a discussion of object oriented programming. I chose to leave that for a later text, since most area builders code for the creativity, not for the computer science theory. In both the intermediate and beginner textbooks, I have chosen only to discuss theory where it is directly applicable to practical LPC programming. For people who are starting out green in LPC and want to code the next great mudlib, perhaps theory would be more useful. But for the purposes of this book, a discussion of object oriented programming is simply a snoozer. I do plan to get heavy into theory with the next textbook.

1.5 Summary

LPC is not difficult to learn. It is a language which, although pathetic compared to any other language for performing most computer language tasks, is incredibly powerful and unequalled for the tasks of building an area in MUD type games. For the beginner, it allows you to easily jump in and code useful objects without even knowing what you are doing. For the intermediate person, it allows you to turn any idea you have into textual virtual reality. And for the advanced person, itÕs object oriented features can allow you to build one of the most popular games on the internet. What you can do is simply limited by how much you know. And learning more does not require a computer science degree.

mud@wl.mud.de