88 At the same time we provide a number of programming concepts, standard templates that can be used for many ECLiPSe programming tasks. A knowledge of these concepts helps the programmer not only to understand existing code more rapidly, but also should lead to standard solutions whenever a new problem has to be solved.
104 The ECLiPSe documentation contains most of the information provided in this tutorial, but presents it in a very different way. Invariably, it describes all features of the system, many of which are only required for quite specific (if important) tasks like developing new constraint engines inside the system. It can be difficult to find which parts of the documentation contains important hints to solve a particular problem. On the other hand, it will be useful to look up each feature in the user manual and/or the reference manual as they occur in the tutorial.
263 \item[transform] We then use these data structures to create new, transformed data in the tranformation part of the application.
269 Once we have decided on a top-level structure, we must consider the input/output arguments of each part. We have to decide which data must be fed into which modules, where new data structures will be created and which other modules require this data. For each piece of information we must identify its source and its possible sinks. Designing these data flows is an iterative process, assigning functionality to modules and making sure that the required information is available. The design aim should be to minimize the amount of information that must be passed across module boundaries and to arrange functions in the correct data flow order, so that all information is produced before it is required in another module.
402 If a system contains many modules, it can be helpful to provide a query which automatically generates the documentation for all files. In RiskWise, there is a module {\it document} \index{document}with an entry point {\it document/0} which creates the complete documentation tree. It uses the built-in predicates {\it icompile/1} and {\it ecis\_to\_htlms/4} to extract the documentation information from the source files and to build the HTML files required. Whenever we add a new module to the source of the application, we have to add its name into the {\it components} list.
428 \item[arguments] In the first alternative, all data are passed in arguments to the query. Multiple items of the same type will usually be represented as lists, with structures to hold different attributes of the different objects. This form has the advantage that each query can be run with a completely new data set without changing the database or creating a new set of files. But debugging data in this form can be more difficult, as there is not direct way to look up some data item. This method also requires work on the Java side to build all the data structures before a call to the ECLiPSe solver. A similar effort is required to develop testing code written in ECLiPSe which exercises the interface.
430 \item[data files] The second alternative is to use data files in a fixed format. The ECLiPSe program then has to read these files and build the internal data structures at the same time. Depending on the format, this may require parsing the input format with definite clause grammars (DCG) \index{DCG}\index{definite clause grammar}(see section \ref{howtousedcgs}), adding to the development effort\footnote{ECLiPSEe 5.4 contains a freeware XML (http://www.xml.org) parser which handles most of the detail of parsing XML files. This makes the use of XML as a data exchange format for ECLiPSe are very exiting new possibility. The parser is described in the ``Third Party Library'' section of the reference manual.}. But as the files can be read and written easily, it is quite simple to create test data sets and to analyze problems by hand. The design for the fixed format may require some extra effort if we want to use the full character set for atoms and strings. A proper quoting mechanism may be required in order to distinguish say a comma separator from a comma contained inside a data field.
436 \item[facts] The last alternative is to store the data as facts \index{fact}in the application. They can then be accessed from any part of the ECLiPSe code quite easily. Testing the code is simple by compiling some data files into the system. The Java interface can also store facts into the database quite easily. But changing the data for a new query can be rather complex, and may require recompiling some data modules.
558 It is tempting to ignore warnings in order to get the code running as quickly as possible. That would be a big mistake. We should eliminate all warnings about singleton variables\index{singleton variable} and missing predicate \index{missing predicate}definitions before continuing. Not only will this lead to the detection of problems in the code at this point, we will also immediately see if new warnings are introduced when we change some part of the program. 
616 When adding new parameters it is important to ensure that they are added to all 
673 It is a matter of style whether to use the first or second variant. For simple iterations, the {\it do} loop is usually more elegant. We can also often use it {\it  inline}\index{inline}, and avoid introducing a new predicate name just to perform some iteration.
754 We can use multiple {\it foreacharg} keywords to scan multiple vectors at the same time, but we cannot use {\it foreacharg} to create terms\index{create terms} (we do not know the functor of the term). If we want to create a new term, we have to generate it with the right functor and arity before the {\it do} loop. The following code segment performs vector addition\index{vector addition} $\vec{C} = \vec{A}+ \vec{B}$.
1630 These primitives are reused for all files, so that adding the code to read a new file format basically just requires some rules defining the format. 
2046 it's required. Always put semicolons at the start of a new line, aligned
2172 \item[nl/1] \index{nl/1}write a new-line to a stream
2173 \item[writeln/2] \index{writeln/2}write a term to a stream, followed by a new-line

Indexes created Thu Aug 29 22:33:21 MDT 2024