Using TeXmacs as an interface

An important feature of TeXmacs is it's ability to communicate with extern systems in shell-like sessions. Typically, it is possible to evaluate commands of an extern computer algebra system inside such a session and display the results in a nice, graphical way. It is also possible to evaluate shell commands and Scheme programs inside such sessions.

1.Creating sessions

A session can be started from the Insert→Session menu. A session consists of a sequence of input and output fields and possible text between them. When pressing return inside an input field of a session, the text inside the environment is evaluated and the result is displayed in an output field.

When entering a command in a session, the application attempts to execute it. Several commands may be launched concurrently in the same document, but the output will only be active in the session where the cursor is and at the place of the cursor. Therefore, we recommend to use different buffers for parallel executions.

For each type of extern application, one may choose between sharing a single process by different sessions, or launching a separate process for each different session. More precisely, when inserting a session using Insert→Session→Other, you may specify both a “session type” (Shell, Pari, Maxima, etc.) and a “session name” (the default name is “default”). Sessions with different names correspond to different processes and sessions with the same name share a common process.

In order to finish the process which underlies a given session, you may use Session→Close session. When pressing return in the input of a non-connected system, the system will be restarted automatically. You may also use Session→Interrupt execution in order to interrupt the execution of a command. However, several applications do not support this feature.

2.Editing sessions

Inside input fields of sessions, the cursor keys have a special meaning: when moving upwards or downwards, you will move to previous or subsequent input fields. When moving to the left or to the right, you will never leave the input field; you should rather use the mouse for this.

Some facilities for editing input, output and text fields are available in the Session→Insert fields and Session→Remove fields menus. Most operations directly apply to matching input/output fields. Optionally, an additional explanatory text field can be associated to an input field using Session→Insert fields→Insert text field. Keyboard shortcuts for inserting fields are A-up (insert above) and A-down. Keyboard shortcuts for removing matching text/input/output fields are A-backspace (remove backwards) and A-delete (remove current fields).

It is possible to create “subsessions” using Session→Insert fields→Fold input field or A-right. In that case, the current text/input/output field becomes the body of an unfolded subsession. Such a subsession consists of an explanatory text together with a sequence of text/input/output fields. Subsessions can be folded and unfolded using M-A-up resp. M-A-down. Subsessions have a nice rendering on the screen when using the varsession package in Document→Use package→Program.

Other useful editing operations for text/input/output fields are Session→Remove fields→Remove all output fields, which is useful for creating a demo sessions which will be executed later on, and Session→Split session, which can be used for splitting a session into parts for inclusion into a paper.

3.Selecting the input method

By default, TeXmacs will attempt to evaluate the input field when pressing return. Multiline input can be created using S-return. Alternatively, when selecting the multiline input mode using Session→Input mode→Multiline input, the return key will behave as usual and S-return may be used in order to evaluate the input field. Notice finally that certain systems admit built-in heuristics for testing whether the input has been completed; if not, then the return may behave as usual.

Certain applications allow you to type the mathematical input in a graphical, two dimensional form. This feature can be used by selecting Session→Input mode→Mathematical input. If this feature is available, then it is usually also possible to copy and paste output back into the input. However, it depends on the particular application how well this works.

4.Supported systems

When taking a look at the Insert→Session menu, only those systems which are actually installed on your system will show up. The only exceptions are shell sessions and scheme sessions, which are always available.

Below, you find a short list of free computer algebra systems which have been interfaced with TeXmacs. There also exist interfaces with several proprietary interfaces, but you should look at the documentation of those systems for more information.

4.1.Shell sessions and scheme sessions

In a “shell session” it is possible to evaluate shell commands. All input and output is verbatim. No particular command-line utilities (such as completion mechanisms) have been implemented yet. The output of the shell command is displayed gradually as the program executes.

In a “Scheme session” you can evaluate Guile/Scheme programs. The input should be verbatim text. The input is evaluated and the result is displayed. No gradual output mechanism has been implemented yet for Scheme session.

4.2.Giac

Giac Is A Computer algebra system, which can be downloaded from

    http://www-fourier.ujf-grenoble.fr/~parisse/english.html

4.3.GTybalt

GTybalt is a free computer algebra system which is built on top of GiNaC, CLN and a program to interpret C and C++ commands. For more information, see

    http://www.fis.unipr.it/~stefanw/gtybalt.html

4.4.Macaulay 2

Macaulay 2 is a new software system devoted to supporting research in algebraic geometry and commutative algebra. The software is available now in source code for porting, and in compiled form for Linux, Sun OS, Solaris, Windows, and a few other unix machines. You can get it from

    http://www.math.uiuc.edu/Macaulay2

4.5.Maxima

Maxima is not alone one of the oldest and best computer algebra systems around, it is also one of the only general purpose systems for which there is a free implementation. You can get it from

    http://www.ma.utexas.edu/users/wfs/maxima.html

The supported version is GCL-based Maxima 5.6. For CLisp-based Maxima 5.6, edit your tm_maxima and replace -load by -i. For Maxima 5.9-pre, replace -load by -p. Known problems:

• If you press return when a statement is not complete (typically, terminated by ; or $), the interface will hang.
• If you cause the Lisp break prompt to appear, the interface will hang.
• The command info is not supported (it is defined in the underlying Lisp, and difficult to support portably).
• Some commands in the debugger work, but some (including :c) don't work, nobody knows why.
• The command load sometimes behaves mysteriously.

4.6.Pari

Pari is a software package for computer-aided number theory. It consists of a C library, libpari (with optional assembler cores for some popular architectures), and of the programmable interactive gp calculator. You can download Pari from

    ftp://megrez.math.u-bordeaux.fr/pub/pari

You will need a version newer than Pari-2.1.0 for use from inside TeXmacs (for an already installed Pari-system, type gp –version).

4.7.Qcl

QCL is a high level, architecture independent programming language for quantum computers, with a syntax derived from classical procedural languages like C or Pascal. This allows for the complete implementation and simulation of quantum algorithms (including classical components) in one consistent formalism. The TeXmacs interface is mainly useful for displaying quantum states in a readable way. For more information, see

    http://tph.tuwien.ac.at/~oemer/qcl.html

Starting from 1.0.0.8, TeXmacs supports QCL 0.4.3 or newer. Users of older versions should upgrade.

4.8.Yacas

Yacas is, as it's name suggest, yet another computer algebra system. Things implemented include: arbitrary precision, rational numeric, vector, complex, and matrix computations (including inverses and determinants and solving matrix equations), derivatives, solving, Taylor series, numerical solving (Newtons method), and a lot more non-mathematical algorithms. The language natively supports variables and user-defined functions. There is basic support for univariate polynomials, integrating functions and tensor calculations. You can get Yacas at

    http://www.xs4all.nl/~apinkus/yacas.html