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@node Introduction, Installation, Top, Top
@chapter Introduction
Geiser is an Emacs environment to hack and have fun in Scheme. If that's
enough for you, see @ref{Installation} to get it running and
@ref{Quick start} for the fun.
@menu
* Manifesto::
* Modus operandi::
* Showing off::
@end menu
@node Manifesto, Modus operandi, Introduction, Introduction
@section Manifesto
Geiser is a collection of Emacs major and minor modes that conspire with
one or more Scheme interpreters to keep the Lisp Machine Spirit alive.
It draws inspiration (and a bit more) from environments such as Common
Lisp's Slime, Factor's FUEL, Squeak or Emacs itself, and does its best
to make Scheme hacking inside Emacs (even more) fun. Or, to be precise,
what i consider fun. Geiser is thus my humble contribution to the
dynamic school of expression, and a reaction against what i perceive as
a derailment, in modern times, of standard Scheme towards the static
camp. Because i prefer growing and healing to poking at corpses, the
continuously running Scheme interpreter takes the center of the stage in
Geiser. A bundle of Elisp shims orchestrates the dialog between the
Scheme interpreter, Emacs and, ultimately, the programmer (that means,
hopefully, you). It asks the live image for metadata in real time,
providing access to them using, as much as possible, standard Emacs
idioms.
That's the dreal.
@node Modus operandi, Showing off, Manifesto, Introduction
@section Modus operandi
As already mentioned, Geiser relies on a running Scheme process to
obtain the information it makes accessible to the programmer. There's
little effort, on the Elisp side, to understand, say, the module system
used by the Scheme implementation at hand; instead, a generic interface
between the two worlds is defined, and each supported Scheme includes a
library implementing that API, together with some wee shims in Elisp
allowing the reuse of the Emacs-side framework, which constitutes the
bulk of the code.
While being as generic as possible, the Scheme-Elisp interface makes
some assumptions about the capabilities and interaction mode of the
corresponding REPL. In particular, Geiser expects the latter to support
namespaces in the form of a module system, and to provide a well defined
way to establish the REPL's current namespace (or module), as well as
the current's file module (or namespace). Thus, all evaluations
performed by Geiser either in the REPL or in a source code buffer happen
in the context of the current namespace. Every time you switch to a
different file, you're switching namespaces automatically; at the REPL,
you must request the switch explicitly (usually just using means
provided by the Scheme implementation itself).
If your favourite scheme supports the above modus operandi, it has all
that's needed for a bare-bones Geiser mode. But Geiser can, and will,
use any metadata available: procedure arities and argument lists to
display interactive help, documentation strings, location information to
jump to definitions, export lists to provide completion, and so on and
so forth. Although this is not an all-or-none proposition (Geiser can
operate with just part of that functionality available), i've
concentrated initially in supporting those Schemes with the richest (to
my knowledge) introspection capabilities, namely, Guile and Racket.
@node Showing off, , Modus operandi, Introduction
@section Showing off
When working with a fully conniving Scheme, Geiser can offer the
following functionality:
@itemize @bullet
@item
Form evaluation in the context of the current file's module.
@item
Macro expansion.
@item
File/module loading and/or compilation.
@item
Namespace-aware identifier completion (including local bindings, names
visible in the current module, and module names).
@item
Autodoc: the echo area shows information about the signature of the
procedure/macro around point automatically.
@item
Jump to definition of identifier at point.
@item
Access to documentation (including docstrings when the implementation
provides it).
@item
Listings of identifiers exported by a given module.
@item
Listings of callers/callees of procedures.
@item
Rudimentary support for debugging (when the REPL provides a debugging)
and error navigation.
@item
Support for multiple, simultaneous REPLs.
@end itemize
In the following sections, i'll try to explain what these features
actually are (i'm just swanking here), and how to use them for your
profit. But, before that, let's see how to install Geiser.
@c Local Variables:
@c mode: texinfo
@c TeX-master: "geiser"
@c End:
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