---
layout: doc
title: general / lpc
---
# lpc

- What is LPC?

LPC is the language in which FluffOS (and other LPmud driver) objects are
written. LPC stands for Lars Pensjö C. As one might surmise from the name,
LPC is based on the syntax of C. LPC provides the C while loop, for loop,
if statement, switch statement, a variant of `sscanf()`, and integer data type,
(LPC also provides other data types not in C such as the object and the
mapping). LPC uses C's syntax for defining and calling functions and for
declaring variables. Note that LPC's version of the string datatype is
much different from that provided by C. See the LPC tutorial on syntax
and language constructs for more information.

Here are some differences between LPC and C:

There is no need for a function named `main()` in LPC objects (although there
is one called `create()`).

The efuns (or system calls) provided by the gamedriver are different than
those typically found in the C library (libc.a).

There is no `malloc()`. However, there is an `allocate(int value)` efun that
lets space be allocated for arrays. Note that the argument to `allocate()`
is not in units of bytes, but rather in units of elements.

Memory is never explicitly deallocated. The gamedriver keeps track of
how many times a given piece of data has been referenced. When the
reference count goes to zero (when no object has a copy of that variable),
then the space used by the variable is reclaimed (garbage collected).

The string data type in LPC is closer to that provided by BASIC than that
provided by C. Strings are not declared as arrays of characters but rather
as a basic intrinsic type. Strings may be concatenated using the `+` operator.

For example, the LPC statements:

```c
string ack;

ack = foo + bar;
```

are equivalent to the C statements:

```c
char *ack;

ack = (char *)malloc(strlen(foo) + 1);
strcpy(ack, foo);
ack = (char *)realloc(ack, strlen(ack) + strlen(bar) + 1);
strcat(ack, bar);
```

LPC is an interpreted language (however it is compiled into an internal
compact tokenized form before being interpreted).

LPC has no unions, but it does provide class types (also called structs),
which group a fixed set of named members much like a C structure (see the
[classes documentation](../../lpc/types/classes.md)). The mapping datatype
can also serve as an effective
substitute for structures in some situations. Note that the `->` operator serves
two purposes in LPC: a call to another object (`call_other()`), and access to a
class member.

`sscanf()` does not work in the same way as in C. Arguments to `sscanf()` need
not be pointers (since LPC does not have the explicit pointer data type). Also,
`sscanf(arg, "%s %s", str1, str2)` does not operate as the C programmer would
expect. In C, the first word of `arg` would be copied into `str1` and the
second word of `arg` into `str2`. In LPC, the first word is copied into `str1`
and the _remainder_ of `arg` is copied into `str2`.
