Functional MetaPost is a frontend to the MetaPost language http://www.tug.org/metapost.html by John Hobby. Users write their graphics as Haskell programs, which then emit MetaPost code that can be compiled into encapsulated PostScript files and smoothly included into e.g. LaTeX.

Your best bet for documentation are the German-language documents

• http://cryp.to/funcmp/legacy-doc/Thesis.ps and
• http://cryp.to/funcmp/legacy-doc/Tutorial.ps;

or these (incomplete) English translations:

• http://cryp.to/funcmp/legacy-doc/Manual_eng.ps,
• http://cryp.to/funcmp/legacy-doc/Thesis_eng.ps,
• http://cryp.to/funcmp/legacy-doc/Tutorial_eng.ps.