form-utils

Useful accessories to Jos Vermaseren's computer algebra system FORM. (See https://www.nikhef.nl/~form/ for information about FORM.)

FORM is wonderful and powerful, but sometimes a bit inconvenient to use. As an avid FORM user, I have started to make some custom things to make its use a bit smoother.

Syntax highlighting

As far as I know, the only editor in widespread use that supports FORM syntax highlighing is Vim. GitHub doesn't recognise it, but someday I dream of adding it to Linguist. For Gnome-based editors, some wonderful person (https://github.com/vsht/form.lang) has written a syntax highlighting specification. Here, I do the same for KDE.

To use, put the file form.xml provided here into

$HOME/.local/share/org.kde.syntax-highlighting/syntax/

and you're good to go: FORM will show up under the "scientific" language category in any editor/IDE that uses Katepart as the underlying text editor. This will also make the editor automatically recognise .frm and .prc files as FORM files, as well as .hf, which is one possible convention for FORM header files (FORM doesn't specify the extension for these, but .hf makes for easier distinction from C header files).

Multibrackets

FORM's bracket command is great for increasing the readability of the output, but it is unfortunately limited to one level. Therefore, if

bracket a,b,(...),z, F; 
print +s;
.end

results in the output

expression =  
   + a*b*(...)*z*F(aaa) * ( 
     long expression 
   )
   + a*b*(...)*z*F(bbb) * ( 
      another long expression 
   )
   ...
   + a*b*(...)*z*F(zzz) * (
      yet another long expression 
   );

the long a*b*(...)*z makes all lines unnecessarily crowded, but removing either a,b,(...),z or F from the bracket would make them appear on each line in the long expressions. The only other solution is to restructure your expressions manually, do some clumsy and limited tricks with the dum_ function, or bite the bullet and read the expressions as-is.

This problem is resolved in a rather hacky way by including multibrackets. After making multibracket and putting things in the relevant include paths, simlply put

#include multibracket.hf

somewhere in your FORM program where declarations are allowed, and then replace the bracket keyword with the macro `multibracket'. Leave the other arguments as they are. Then pipe your FORM output as follows:

> form your_program.frm | multibracket a,b,(...),z F

and the output will instead look like

expression = 

   + a*b*(...)*z * (
      + F(aaa) * (
         long expression
      )
      + F(bbb) * (
         another long expression
      )
      ...
      + F(zzz) * (
         yet another long expression
      )
   );

which is vastly more readable. This works in general: each level of bracketing is given as a separate argument to multibracket, and symbols on the same level are separated by commas (and/or spaces, if the argument is quoted). FORM's '...' syntax can be used (e.g. multibracket "a1,...,a55" "<f1x>,...,<f7x>"), although quotes may be necessary to avoid confusing the shell. Set notation can not be used, although it may be supported in the future. If a symbol occurs multiple times, only its first appearance counts.

All symbols that are supplied to the extermal multibracket command must also be supplied as arguments to the `multibracket' macro. All FORM output that is not affected by the macro is printed without being changed. All print options (+s etc) are supported, but not options and abbreviations of bracket, nor antibracket.

The tags needed for multibracket formatting are not automatically removed. You need to use the macro `nmultibracket', which works as an executable satement, to remove them so that expressions can subsequently be printed without multibracketing, if you so wish.

KNOWN BUG: If the outside-the-bracket part is so long that FORM line-wraps it (i.e. if the " * (" ends up on a different line than the " + ", multibracket will not work (or rather, it will appear to work but will fail to balance parentheses). To avoid this, never multibracket FORM log filed (which are hard-wrapped) but instead feed FORM output directly into it, or via a file written on your conditions.