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General Information

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


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

Reference Manuals

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


 o Eli library routines
 o Specification Module Library

Translation Tasks

 o Lexical analysis specification
 o Syntactic Analysis Manual
 o Computation in Trees


 o LIGA Control Language
 o Debugging Information for LIDO
 o Graphical ORder TOol

 o FunnelWeb User's Manual

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

 o Generating Unparsing Code

 o Monitoring a Processor's Execution


 o System Administration Guide

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LIDO -- Computations in Trees

Language processors generated by Eli consist of a structuring phase and a transformation phase. The first reads the input, checks whether its structure fulfills the language requirements and builds a tree representing that structure. The transformation phase performs any kind of computations on such trees necessary for analysis of the input structure and for computing some output as required by the language processor tasks. Both phases are generated from user supplied specifications.

This document introduces the techniques used to specify the transformation phase. Its central concepts are computations in trees. The subsequent sections introduce the most important techniques and their notation in the specification language LIDO on the base of very simple examples.

Tree Structure to Early Computations During Tree Construction should be read in that order to get a complete overview. It should be pointed out, that this document is not intended to define the language LIDO. The LIDO Reference Manual should be consulted for specific questions on language constructs. It also describes facilities which increase the expressive power of LIDO far beyond the level introduced here. See LIDO -- Reference Manual. Many common subtasks of the transformation phase need not be solved by writing LIDO specifications from scratch. Reusable solutions can be obtained from Eli's module library. See ModLib - Specification Module Library.

Interactions within Eli of this document describes how to use LIDO specifications within Eli, how they interact with other specifications and how to get more information when errors are reported on the specification. The first part ( Supplying Tree Computation Specifications to Eli to Implementing Tree Computations) should be read while examples are practically exercised. Specification Errors should be consulted initially when errors occur that can not be immediately traced and corrected.