Indexed Generators¶

class sage.structure.indexed_generators.IndexedGenerators(indices, prefix='x', **kwds)

Bases: object

Abstract base class for parents whose elements consist of generators indexed by an arbitrary set.

Options controlling the printing of elements:

• prefix – string, prefix used for printing elements of this module (optional, default ‘x’). With the default, a monomial indexed by ‘a’ would be printed as x['a'].

• latex_prefix – string or None, prefix used in the $$\LaTeX$$ representation of elements (optional, default None). If this is anything except the empty string, it prints the index as a subscript. If this is None, it uses the setting for prefix, so if prefix is set to “B”, then a monomial indexed by ‘a’ would be printed as B_{a}. If this is the empty string, then don’t print monomials as subscripts: the monomial indexed by ‘a’ would be printed as a, or as [a] if latex_bracket is True.

• bracketNone, bool, string, or list or tuple of strings (optional, default None): if None, use the value of the attribute self._repr_option_bracket, which has default value True. (self._repr_option_bracket is available for backwards compatibility. Users should set bracket instead. If bracket is set to anything except None, it overrides the value of self._repr_option_bracket.) If False, do not include brackets when printing elements: a monomial indexed by ‘a’ would be printed as B'a', and a monomial indexed by (1,2,3) would be printed as B(1,2,3). If True, use “[” and “]” as brackets. If it is one of “[”, “(”, or “{”, use it and its partner as brackets. If it is any other string, use it as both brackets. If it is a list or tuple of strings, use the first entry as the left bracket and the second entry as the right bracket.

• latex_bracket – bool, string, or list or tuple of strings (optional, default False): if False, do not include brackets in the LaTeX representation of elements. This option is only relevant if latex_prefix is the empty string; otherwise, brackets are not used regardless. If True, use “left[” and “right]” as brackets. If this is one of “[”, “(”, “\{”, “|”, or “||”, use it and its partner, prepended with “left” and “right”, as brackets. If this is any other string, use it as both brackets. If this is a list or tuple of strings, use the first entry as the left bracket and the second entry as the right bracket.

• scalar_mult – string to use for scalar multiplication in the print representation (optional, default “*”)

• latex_scalar_mult – string or None (default: None), string to use for scalar multiplication in the latex representation. If None, use the empty string if scalar_mult is set to “*”, otherwise use the value of scalar_mult.

• tensor_symbol – string or None (default: None), string to use for tensor product in the print representation. If None, use sage.categories.tensor.symbol and sage.categories.tensor.unicode_symbol.

• sorting_key – a key function (default: lambda x: x), to use for sorting elements in the output of elements

• sorting_reverse – bool (default: False), if True sort elements in reverse order in the output of elements

• string_quotes – bool (default: True), if True then display string indices with quotes

Note

These print options may also be accessed and modified using the print_options() method, after the parent has been defined.

EXAMPLES:

We demonstrate a variety of the input options:

sage: from sage.structure.indexed_generators import IndexedGenerators
sage: I = IndexedGenerators(ZZ, prefix='A')
sage: I._repr_generator(2)
'A[2]'
sage: I._latex_generator(2)
'A_{2}'

sage: I = IndexedGenerators(ZZ, bracket='(')
sage: I._repr_generator(2)
'x(2)'
sage: I._latex_generator(2)
'x_{2}'

sage: I = IndexedGenerators(ZZ, prefix="", latex_bracket='(')
sage: I._repr_generator(2)
'[2]'
sage: I._latex_generator(2)
\left( 2 \right)

sage: I = IndexedGenerators(ZZ, bracket=['|', '>'])
sage: I._repr_generator(2)
'x|2>'

indices()

Return the indices of self.

EXAMPLES:

sage: F = CombinatorialFreeModule(QQ, ['a', 'b', 'c'])
sage: F.indices()
{'a', 'b', 'c'}

prefix()

Return the prefix used when displaying elements of self.

EXAMPLES:

sage: F = CombinatorialFreeModule(QQ, ['a', 'b', 'c'])
sage: F.prefix()
'B'

sage: X = SchubertPolynomialRing(QQ)
sage: X.prefix()
'X'

print_options(**kwds)

Return the current print options, or set an option.

INPUT: all of the input is optional; if present, it should be in the form of keyword pairs, such as latex_bracket='('. The allowable keywords are:

• prefix

• latex_prefix

• bracket

• latex_bracket

• scalar_mult

• latex_scalar_mult

• tensor_symbol

• string_quotes

• sorting_key

• sorting_reverse

See the documentation for IndexedGenerators for descriptions of the effects of setting each of these options.

OUTPUT: if the user provides any input, set the appropriate option(s) and return nothing. Otherwise, return the dictionary of settings for print and LaTeX representations.

EXAMPLES:

sage: F = CombinatorialFreeModule(ZZ, [1,2,3], prefix='x')
sage: F.print_options()
{...'prefix': 'x'...}
sage: F.print_options(bracket='(')
sage: F.print_options()
{...'bracket': '('...}

sage.structure.indexed_generators.parse_indices_names(names, index_set, prefix, kwds=None)

Parse the names, index set, and prefix input, along with setting default values for keyword arguments kwds.

OUTPUT:

The triple (N, I, p):

• N is the tuple of variable names,

• I is the index set, and

• p is the prefix.

This modifies the dictionary kwds.

Note

When the indices, names, or prefix have not been given, it should be passed to this function as None.

Note

For handling default prefixes, if the result will be None if it is not processed in this function.

EXAMPLES:

sage: from sage.structure.indexed_generators import parse_indices_names
sage: d = {}
sage: parse_indices_names('x,y,z', ZZ, None, d)
(('x', 'y', 'z'), Integer Ring, None)
sage: d
{}
sage: d = {}
sage: parse_indices_names('x,y,z', None, None, d)
(('x', 'y', 'z'), {'x', 'y', 'z'}, '')
sage: d
{'bracket': False, 'string_quotes': False}
sage: d = {}
sage: parse_indices_names(None, ZZ, None, d)
(None, Integer Ring, None)
sage: d
{}

sage: d = {'string_quotes':True, 'bracket':'['}
sage: parse_indices_names(['a','b','c'], ZZ, 'x', d)
(('a', 'b', 'c'), Integer Ring, 'x')
sage: d
{'bracket': '[', 'string_quotes': True}
sage: parse_indices_names('x,y,z', None, 'A', d)
(('x', 'y', 'z'), {'x', 'y', 'z'}, 'A')
sage: d
{'bracket': '[', 'string_quotes': True}

sage.structure.indexed_generators.split_index_keywords(kwds)

Split the dictionary kwds into two dictionaries, one containing keywords for IndexedGenerators, and the other is everything else.

OUTPUT:

The dictionary containing only they keywords for IndexedGenerators. This modifies the dictionary kwds.

Warning

This modifies the input dictionary kwds.

EXAMPLES:

sage: from sage.structure.indexed_generators import split_index_keywords
sage: d = {'string_quotes': False, 'bracket': None, 'base': QQ}
sage: split_index_keywords(d)
{'bracket': None, 'string_quotes': False}
sage: d
{'base': Rational Field}

sage.structure.indexed_generators.standardize_names_index_set(names=None, index_set=None, ngens=None)

Standardize the names and index_set inputs.

INPUT:

• names – (optional) the variable names

• index_set – (optional) the index set

• ngens – (optional) the number of generators

If ngens is a negative number, then this does not check that the number of variable names matches the size of the index set.

OUTPUT:

A pair (names_std, index_set_std), where names_std is either None or a tuple of strings, and where index_set_std is a finite enumerated set. The purpose of index_set_std is to index the generators of some object (e.g., the basis of a module); the strings in names_std, when they exist, are used for printing these indices. The ngens

If names contains exactly one name X and ngens is greater than 1, then names_std are Xi for i in range(ngens).