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The LPC Reference Manual

1. Introduction

1.1. Purpose

This document is a formal description of the LPC programming language. The LPC programming language is derived from C and named after its primary creator, Lars Pensjö. Several dialects of LPC exist; the programming language described here is the one used in Dworkin's Generic Driver (DGD) version 1.1.

1.2. History

2. Environment

3. Language

In the syntax notation of this document, syntactic catagories are indicated by italic type.

3.1. Lexical elements

3.1.1. Tokens

A token is the minimal lexical element of the language. The categories of tokens are: identifiers, keywords, constants, operators and punctuators. Tokens are separated by white space: blanks, horizontal and vertical tabs, newlines, carriage returns, formfeeds and comments.

3.1.2. Comments

A comment is a sequence of characters starting with the characters /* and terminated by the characters */. All characters in between are part of the comment. Comments count as whitespace separating tokens, and may not be nested. The sequence /* does not start a comment if it is part of a string.

3.1.3. Identifiers

An identifier is an arbitrary long sequence of letters, digits and underscores. The first character must be a letter or underscore. Upper- and lower-case letters are different. Only the first 1023 characters of identifiers are significant.

3.1.4. Keywords

The following identifiers are reserved for use as keywords:

	atomic      do          int         return      void
	break       else        mapping     rlimits     while
	case        float       mixed       static
	catch       for         nomask      string
	continue    if          object      switch
	default     inherit     private     varargs

The keyword atomic is reserved, but currently unused.

3.1.5. Constants

A constant is either an integer constant, floating constant, string constant or character constant.

3.1.5.1. Integer Constants

An integer constant is a decimal constant, octal constant or hexadecimal constant.

A sequence of digits is taken to be a decimal constant (base ten) unless it begins with 0. A sequence of digits starting with 0 and not including 8 or 9 is an octal constant (base 8). A sequence of digits and upper- or lower-case letters in range A through F, preceded by 0x or 0X is a hexadecimal constant (base 16, where A through F have the decimal values 10 through 15).

Integer constants are represented by 32 bit 2's complement arithmetic, and range from -2147483648 through 2147483647. It is an error to specify a decimal constant that is too large to be represented. Octal constants and hexadecimal constants, when too large, are truncated to the lower 32 bits.

3.1.5.2. Floating constants

A floating constant consists of an integer part, a decimal point, a fraction part, and an exponent part, consisting of an e or E and an optionally signed integer exponent. Either the integer part or the fraction part, but not both, may be missing. Either the decimal point and fraction part, or the exponent part, but not both, may be missing.

Floating constants represent a floating point number in the range of -1.79769313485E308 through 1.79769313485E308, the smallest possible number being -2.22507385851E-308. It is an error to specify a floating constant that is too large to be represented. Numbers which are too small are flushed to zero.

3.1.5.3. String constants

A string constant is a sequence of zero or more characters enclosed in double quotes. All characters, with the exception of newline, can be used in a string constant. A backslash character \ introduces an escape sequence, which consists of at least 2 and at most 5 characters (including the backslash), and which is translated into a single character in the string. The following escape sequences can be used:

	\a = 007 (bell)			\o
	\b = 010 (backspace)		\oo
	\f = 014 (form feed)		\ooo
	\n = 012 (newline)		\xh
	\r = 015 (carriage return)	\xhh
	\t = 011 (horizontal tab)	\xhhh
	\v = 013 (vertical tab)		\c

The value of \a, \b, \f, \n, \r, \t and \v is the octal value shown. \o, \oo and \ooo constitute an integer of at most 3 octal digits, the octal value of which specifies a single character. \xh, \xhh and \xhhh constitute an integer of at most 3 hexadecimal digits, the hexadecimal value of which specifies a single character. All other escape sequences \c specify the character c (any character except a, b, f, n, r, t, v, x, or a digit), which itself is not interpreted in any special way.

3.1.5.4. Character constants

A character constant consists of a single character or escape sequence, enclosed in single quotes. All characters except newline can be used. Escape sequences are handled as with string constants.

3.1.6. Operators

The following are operators:

	[   ]   (   )   ->
	++  --  +   -   ~   !   ... catch
	*   /   %   <<  >>  <   >   <=  >=  ==  !=  &   ^   |   &&  ||
	?   :
	=   *=  /=  %=  +=  -=  <<= >>= &=  ^=  |=
	,