Macaulay2 » Documentation
Packages » Macaulay2Doc » The Macaulay2 language » Thing » Nothing
next | previous | forward | backward | up | index | toc

# Nothing -- the empty class

## Description

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

### Menu

- null -- the unique member of the empty class

## Types of Nothing:

- InexactNumber'

## Functions and methods returning an object of class Nothing:

- addCancelTask(Task,Task) -- specify that the completion of one task triggers the cancellation of another
- addDependencyTask(Task,Task) -- schedule a task, but ensure that it will not run until another task finishes
- addStartTask(Task,Task) -- schedule a task upon completion of another
- cancelTask(Task) -- stop a task
- `echoOff(File)` -- see echoOff -- turn off echoing
- `echoOn(File)` -- see echoOn -- turn on echoing
- `kill(File)` -- see kill -- kill a process
- kill(ZZ) -- kill a process
- linkFile(String,String) -- make a new link to a file
- `remove(Database,String)` -- see remove -- remove an entry from a mutable hash table, list, or database
- `remove(HashTable,Thing)` -- see remove -- remove an entry from a mutable hash table, list, or database
- `remove(MutableList,ZZ)` -- see remove -- remove an entry from a mutable hash table, list, or database
- `scanPairs(HashTable,Function)` -- see scanPairs -- apply a function to the pairs in a hash table
- `scanPairs(Thing,Function)` -- see scanPairs -- apply a function to the pairs in a hash table

## Methods that use an object of class Nothing:

- `Nothing #? Thing` -- see #? -- check existence of value in a list, hash table, database, or string
- `concatenate(Nothing)` -- see concatenate -- join strings
- `getWWW(String,Nothing)` -- see getWWW -- get a web page
- `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
- `info(Nothing)` -- see info -- convert hypertext to info format
- `locate(Nothing)` -- see locate -- locate source code
- `Manipulator Nothing` -- see Manipulator -- the class of all file manipulators
- `map(Module,Nothing,RingMap,List)` -- see map(Module,Module,RingMap,Matrix) -- homomorphism of modules over different rings
- `map(Module,Nothing,RingMap,Matrix)` -- see map(Module,Module,RingMap,Matrix) -- homomorphism of modules over different rings
- 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 (pullback) of image of a map (low level version)
- `modulo(Nothing,Matrix)` -- see modulo -- find the pre-image (pullback) of image of a map (low level version)
- `package(Nothing)` -- see package -- get containing package
- `part(Nothing,Nothing,RingElement)` -- see part -- select terms of a polynomial by degree(s) or weight(s)
- `part(Nothing,Nothing,VisibleList,RingElement)` -- see part -- select terms of a polynomial by degree(s) or weight(s)
- `part(Nothing,ZZ,RingElement)` -- see part -- select terms of a polynomial by degree(s) or weight(s)
- `part(Nothing,ZZ,VisibleList,RingElement)` -- see part -- select terms of a polynomial by degree(s) or weight(s)
- `part(ZZ,Nothing,RingElement)` -- see part -- select terms of a polynomial by degree(s) or weight(s)
- `part(ZZ,Nothing,VisibleList,RingElement)` -- see part -- select terms of a polynomial by degree(s) or weight(s)
- `Nothing << Manipulator` -- see printing to a file -- print to a file
- `Nothing << Thing` -- see printing to a file -- print to a file
- `sublists(VisibleList,Function,Function,Nothing)` -- see sublists -- process interspersed subsequences of a visible list
- `sublists(VisibleList,Function,Nothing)` -- see sublists -- process interspersed subsequences of a visible list
- `sublists(VisibleList,Function,Nothing,Function)` -- see sublists -- process interspersed subsequences of a visible list
- `sublists(VisibleList,Function,Nothing,Nothing)` -- see sublists -- process interspersed subsequences of a visible list
- `submatrix'(Matrix,Nothing,Nothing)` -- see submatrix' -- exclude rows and/or columns of a matrix
- `submatrix'(Matrix,Nothing,VisibleList)` -- see submatrix' -- exclude rows and/or columns of a matrix
- `submatrix'(Matrix,VisibleList,Nothing)` -- see submatrix' -- exclude rows and/or columns of a matrix
- `subquotient(Matrix,Nothing)` -- see subquotient -- make a subquotient module
- `subquotient(Module,Matrix,Nothing)` -- see subquotient -- make a subquotient module
- `subquotient(Module,Nothing,Matrix)` -- see subquotient -- make a subquotient module
- `subquotient(Module,Nothing,Nothing)` -- see subquotient -- make a subquotient module
- `subquotient(Nothing,Matrix)` -- see subquotient -- make a subquotient module
- `symmetricAlgebra(Nothing,Nothing,Matrix)` -- see symmetricAlgebra -- the symmetric algebra of a module
- `symmetricAlgebra(Nothing,Ring,Matrix)` -- see symmetricAlgebra -- the symmetric algebra of a module
- `symmetricAlgebra(Ring,Nothing,Matrix)` -- see symmetricAlgebra -- the symmetric algebra of a module
- truncate(Nothing,InfiniteNumber,Matrix) (missing documentation)
- truncate(Nothing,List,Matrix) (missing documentation)
- truncate(Nothing,ZZ,Matrix) (missing documentation)
- `urlEncode(Nothing)` -- see urlEncode -- URL encoding

## For the programmer

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

The source of this document is in /build/macaulay2-88fgJW/macaulay2-1.25.11+ds/M2/Macaulay2/packages/Macaulay2Doc/ov_types.m2:552:0.