Nothing -- the empty class

Description

This class is useful for representing the class of an argument which is missing. It is also used as the parent for those things which are not themselves types, i.e., which do not have instances.

Functions and methods returning an object of class Nothing :

echoOff(File), see echoOff -- turn off echoing
echoOn(File), see echoOn -- turn on echoing
kill(File), see kill -- kill a process
linkFile(String,String) -- make a new link to a file
remove(HashTable,Thing), see remove -- remove an entry from a hash table
scan(BasicList,Function) -- apply a function to each element of a list
scan(ZZ,Function) -- apply a function to 0 .. n-1
scanPairs(HashTable,Function) -- apply a function to pairs in a hash table

Methods that use an object of class Nothing :

concatenate(Nothing), see concatenate -- join strings
Nothing << Manipulator, see File << Thing -- print to a file
Nothing << Thing, see File << Thing -- print to a file
getWWW(String,Nothing), see getWWW -- get a web page
homology(Nothing,Sequence) -- missing documentation
inducedMap(Module,Nothing,Matrix), see inducedMap(Module,Module,Matrix) -- compute the induced map
inducedMap(Nothing,Module,Matrix), see inducedMap(Module,Module,Matrix) -- compute the induced map
inducedMap(Nothing,Nothing,Matrix), see inducedMap(Module,Module,Matrix) -- compute the induced map
inducesWellDefinedMap(Module,Nothing,Matrix), see inducesWellDefinedMap -- whether a map is well defined
inducesWellDefinedMap(Nothing,Module,Matrix), see inducesWellDefinedMap -- whether a map is well defined
inducesWellDefinedMap(Nothing,Nothing,Matrix), see inducesWellDefinedMap -- whether a map is well defined
locate(Nothing), see locate -- locate source code
Manipulator Nothing -- missing documentation
map(Module,Nothing,List) -- create a matrix by giving a doubly nested list of ring elements
map(Module,Nothing,Matrix) -- recast a matrix to have a new target, and a free module as source
modulo(Matrix,Nothing), see modulo -- find the pre-image of a map (low level version)
modulo(Nothing,Matrix), see modulo -- find the pre-image of a map (low level version)
sublists(VisibleList,Function,Function,Nothing), see sublists -- process interspersed sublists of a list
sublists(VisibleList,Function,Nothing), see sublists -- process interspersed sublists of a list
sublists(VisibleList,Function,Nothing,Function), see sublists -- process interspersed sublists of a list
sublists(VisibleList,Function,Nothing,Nothing), see sublists -- process interspersed sublists of a list
submatrix'(Matrix,Nothing,VisibleList) -- missing documentation
submatrix'(Matrix,VisibleList,Nothing) -- missing documentation
submatrix(Matrix,Nothing,VisibleList), see submatrix(Matrix,VisibleList,VisibleList) -- select part of a matrix
submatrix(Matrix,VisibleList,Nothing), see submatrix(Matrix,VisibleList,VisibleList) -- select part of a matrix
subquotient(Module,Matrix,Nothing) -- missing documentation
subquotient(Module,Nothing,Matrix) -- missing documentation
subquotient(Module,Nothing,Nothing) -- missing documentation

Fixed objects of class Nothing :

null -- the unique member of the empty class

For the programmer

The object Nothing is a type, with ancestor class Thing.