++ -- a binary operator, usually used for direct sum

Ways to use ++ :

• BettiTally ++ BettiTally, see BettiTally -- the class of all Betti tallies
• ChainComplex ++ ChainComplex -- direct sum
• ChainComplexMap ++ ChainComplexMap, see ChainComplex ++ ChainComplex -- direct sum
• GradedModule ++ GradedModule, see ChainComplex ++ ChainComplex -- direct sum
• CoherentSheaf ++ CoherentSheaf -- direct sum of coherent sheaves
• GradedModuleMap ++ GradedModuleMap, see Matrix ++ Matrix -- direct sum of maps
• Matrix ++ Matrix -- direct sum of maps
• Matrix ++ RingElement, see Matrix ++ Matrix -- direct sum of maps
• RingElement ++ Matrix, see Matrix ++ Matrix -- direct sum of maps
• RingElement ++ RingElement, see Matrix ++ Matrix -- direct sum of maps
• GradedModule ++ Module, see Module ++ Module -- direct sum of modules
• Module ++ GradedModule, see Module ++ Module -- direct sum of modules
• Module ++ Module -- direct sum of modules
• Option ++ Option -- missing documentation

For the programmer

The object ++ is a keyword.

         X ++ Y := (x,y) -> ...