_

x_i -- a binary operator which is used for various mathematical operations that are customarily written with subscripts.

A binary method may be installed for x_i with code like 

               X _ Y := (x,i) -> ...
where X is the prospective class of x and Y is the class of i.

Examples where methods have been installed:

  • List _ ZZ -- get an entry from a list
  • Sequence _ ZZ -- get an entry from a sequence
  • List _ List -- get a list of entries from a list or sequence
  • ChainComplex _ ZZ -- get a module from a chain complex
  • Matrix _ ZZ -- get a column from a matrix
  • ChainComplexMap _ ZZ -- get a component from a map of chain complexes
  • Matrix _ Sequence -- get an entry from a matrix
  • Matrix _ List -- get some columns from a matrix
  • RingElement _ RingElement -- get a coefficient from a polynomial
  • Ring _ ZZ -- get a generator from a ring
  • Module _ ZZ -- get a generator of a module
  • Monoid _ ZZ -- get a generator from a monoid
  • Module _ List -- get a map onto some generators of a module
  • Tor -- Tor functor
  • HH -- homology functor
  • Vector _ ZZ -- get an component from a vector
  • SchurRing _ List -- make an element of a Schur ring

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