Catálogo de publicaciones - libros

OCaml provides a module for dealing with paths and filenames in an operating system (OS)-independent manner (this applies only to files, not to Uniform Resource Identifiers [URIs]). I have had to convert programs from using files to using other sources of input; during one of those conversions, I wondered how nice it would be if OCaml had functions that worked with URIs such as Java. There is a very comprehensive URI module included in the Netstring library. It is a third-party library that is part of the Ocamlnet package. Written by Gerd Stoplmann, this library can be found at http://www.ocaml-programming.de.

Almost everyone can agree that writing proper documentation is very important for programmers, but that this task is often overlooked or done poorly.

OCaml provides a very advanced module system. It is based on the meta-language (ML) module system, and it is similar to systems provided in Modula-3 and Ada as well. The module system is basically a small typed language on top of OCaml that enables a programmer to group values, functions, types, classes, and other modules together.

Everyone knows what spam is, even if they don’t know that it refers to unwanted (and usually advertisement-ridden) email instead of the venerable meat product made by the Hormel Corporation.

In the last Chapter, you built a simple spam detector (well, a simple text classifier that can be used for spam detection). It used an on-disk storage mechanism, which works fine for one person on one machine. However, what if that person uses multiple machines? What if you want to have many people or processes contributing information to the text storage?

You might have heard of Lex and Yacc. Lex, the Lexical Analyzer Generator, is a tool that helps you build programs that are built around regular expressions. Yacc, Yet Another Compiler Compiler, is a program for building interpreters and compilers from grammars that you define. Although you do not have to use these tools together (people often use just Lex or Yacc with a custom lexer), but they are often used together.

Ocamllex and ocamlyacc can be used to build compilers for languages. They also can be used to handle any kind of text file that you might want to parse. Complex log files are places in which ocamllex and ocamlyacc can be used that are not often talked about in the literature.

Objective Caml includes very powerful object-oriented features. Although that might seem somewhat obvious given that “objective” is in the language name, the extent and focus of the object system in OCaml is different from many other object-oriented languages currently in use.

Apurely functional function has no side effects. A purely functional programming language would not allow functions with side effects to be defined. But wait, there’s more! Because functions and algorithms cannot have side effects, variables are immutable and persistent. This persistence is not the same as disk storage or serialization; it means that previous versions of a given value can be retained by the language.

At various points in this book, I noted that OCaml is a functional programming language. Chapter 19 told you that OCaml is not a purely functional programming language and what that lack of purity is about.