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HELIUM.md

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There are three ways of working with Helium, each with their own intended audience. First off, there is the standalone Helium compiler, invoked by running the helium program. It's main purpose is to be called from the more user-friendly interactive tools that are part of the Helium distribution, or to be called from other programs, batch files, scripts or make files. It is not very user-friendly, because you have to tell it everything it needs to know about all over again. To actually execute a program, you need to run lvmrun on the output of helium.

The two other possible ways of working with Helium are by means of texthint and Hint. The former is a text-based interactive environment, much like ghci and hugs, although with fewer capabilities. The advantage of texthint is that is can be used quite easily, and it will be built along with the Helium compiler. We use texthint ourselves to quickly try out a few expressions.

Hint, on the other hand, is an interpreter with a graphical interface. It has buttons to be pushed, and pull-down menus. For the ordinary user, Hint is the best choice. An additional advantage of Hint is that you can teach it to load source files that you are working on into your favourite editor. In this way, you can jump directly to the place in your source file where you made a mistake. The drawback of using Hint is that you need Java and Ant on your system to compile and use it.

For each of the three ways we have a separate manual. The interpreters can pass along parameters of your choice to the Helium compiler, so even if you are planning to use only the interpreters, it is best to start off by reading The Basics of the Helium compiler manual first.

In all cases, the above documentation discuss Helium version 1.7 (including pre-releases). Version 1.7 and higher differ in quite a few places from versions 1.6 and lower.

Other issues of note:

  • Nice features to have in an editor for Helium are:
    • Syntax colouring for Helium/Haskell
    • Command-line parameters for jumping to a column and line
    • Expand existing and new tab characters to spaces.
  • A tour of the Helium Prelude: an overview of almost all of the (non-overloaded) Prelude. Each function is clarified by at least its type, examples of its use and a description.
  • Differences with Haskell '98