General Information

	Eli: Translator Construction Made Easy
	Global Index
	Frequently Asked Questions
	Typical Eli Usage Errors

Tutorials

	Quick Reference Card
	Guide For new Eli Users
	Release Notes of Eli
	Tutorial on Name Analysis
	Tutorial on Scope Graphs
	Tutorial on Type Analysis
	Typical Eli Usage Errors

Reference Manuals

	User Interface
	Eli products and parameters
	LIDO Reference Manual
	Typical Eli Usage Errors

Libraries

	Eli library routines
	Specification Module Library

Translation Tasks

	Lexical analysis specification
	Syntactic Analysis Manual
	Computation in Trees

Tools

	LIGA Control Language
	Debugging Information for LIDO
	Graphical ORder TOol

FunnelWeb User's Manual

	Pattern-based Text Generator
	Property Definition Language
	Operator Identification Language
	Tree Grammar Specification Language
	Command Line Processing
	COLA Options Reference Manual

Generating Unparsing Code

Monitoring a Processor's Execution

Administration

System Administration Guide

Tasks related to input processing

Insert a File into the Input Text

Some processors need to insert the content of an arbitrary file at a specific point in the input text currently being processed. For example, consider the C preprocessor cpp, where the file inclusion command #include "myfile" inserts the content of file myfile at the position of that command in the input text. The Eli Include module supports such a requirement. It can be instantiated without generic parameters by

   $/Input/Include.gnrc :inst

The Include module exports the token processor InclDirective (see Token Processors of Lexical analysis specification), allowing the developer to implement a file inclusion command as a lexical token (see Lexical analysis specification).

To implement the cpp file inclusion command as a lexical token, we add a scanner specification (see Specifications of Lexical analysis specification) to a type-gla file:

   $#include\040+\"  (auxEOL)  [InclDirective]

This scanner specification begins with the regular expression #include\040+\", which matches the beginning of the command (see Regular Expressions of Lexical analysis specification). This regular expression requires at least one space to follow the word include, but allows more spaces to precede the string giving the file name. The last character of the regular expression is the delimiter of the file name string.

The auxiliary scanner auxEOL (see Auxiliary Scanners of Lexical analysis specification) advances the input pointer beyond the end of the line of text containing the command (see Available scanners of Lexical analysis specification). This advance is vital, since the input file can only be changed at a line break.

The token processor InclDirective (see Token Processors of Lexical analysis specification) is exported by the Include module. It first extracts mark, the last character matched by the regular expression (in our case, mark is "). If mark is <, InclDirective assumes that the form of the string is <...>; otherwise it assumes that the string is delimited by mark characters.

Given the above assumption, InclDirective scans the text following the text matching the regular expression for the terminating delimiter. When the scan reaches a space, the terminating delimiter, or the end of the line, the file name is taken as the sequence of scanned characters up to, but not including, that space, terminating delimiter, or end-of-line. The module produces a warning if the terminating delimiter is end-of-line.

Finally, InclDirective seeks the specified file and switches the input pointer to that file, if it can be opened. When the end of that file is reached, the input pointer returns to the file containing the file inclusion command, at the beginning of the line following that command. If the specified file cannot be opened, an operating system report is issued and further input is take from the current file.

Recall that the lexical token was specified as:

   $#include\040+\"  (auxEOL)  [InclDirective]

This specification identifies the lexical token as a comment rather than a basic symbol (see Lexical analysis specification). Because it is a comment, it can be used wherever a comment is allowed in the source text. It may be that the developer wishes to restrict file insertion to specific grammatical constructs. In that case, the lexical token should be identified as a basic symbol by giving it a name:

Insertion: $#include\040+\"  (auxEOL)  [InclDirective]

The basic symbol name Insertion can then be used in the grammar just as any basic symbol name. Incorrectly-placed insertion points will be reported as syntax errors, but the contents of the files specified by the insertion commands will still be inserted at the specified points.