RAQ/gap/structure.gd

## structure.gd RAQ Definitions, generation, and elementary ops and props.

## GAP Categories and representations

## Self-distributivity
# Note these are properties that can and therefore should be defined just at
# the level of MultiplicativeElements and Magmas, hence although the LOOPS
# package defines IsLDistributive and IsRDistributive for quasigroups, they
# would be ambiguous in the case of something like a semiring whose
# multiplicative structure was a quasigroup
# (cf. https://arxiv.org/abs/0910.4760). Hence, we implement them in RAQ with
# new, non-conflicting terms.

# An element that knows that multiplication in its family is left
# self-distributive:
DeclareCategory("IsLSelfDistElement", IsMultiplicativeElement);
DeclareCategoryCollections("IsLSelfDistElement");

# An element that knows that multiplication in its family is right
# self-distributive:
DeclareCategory("IsRSelfDistElement", IsMultiplicativeElement);
DeclareCategoryCollections("IsRSelfDistElement");

# Left self-distributive magmas:
DeclareProperty("IsLSelfDistributive", IsMagma);
InstallTrueMethod(IsLSelfDistributive, 
                  IsMagma and IsLSelfDistElementCollection);

# Right self-distributive magmas:
DeclareProperty("IsRSelfDistributive", IsMagma);
InstallTrueMethod(IsRSelfDistributive, 
                  IsMagma and IsRSelfDistElementCollection);

## Idempotence
# There is already a property IsIdempotent on elements, but to definw
# structures which will automatically be quandles we need a corresponding
# collections category:
DeclareCategoryCollections("IsIdempotent");

# Idempotent magmas, i.e. magmas in which every element is idempotent
DeclareProperty("IsElementwiseIdempotent", IsMagma);
InstallTrueMethod(IsElementwiseIdempotent, IsMagma and IsIdempotentCollection);

## Left and right racks and quandles
DeclareSynonym("IsLeftRack", IsLeftQuasigroup and IsLSelfDistributive);
DeclareSynonym("IsRightRack", IsRightQuasigroup and IsRSelfDistributive);

DeclareSynonym("IsLeftQuandle", IsLeftRack and IsElementwiseIdempotent);
DeclareSynonym("IsRightQuandle", IsLeftRack and IsElementwiseIdempotent);

## One-sided quasigroups and racks and quandles by generators

# Returns the closure of <gens> under * and LeftQuotient;
# the family of elements of M may be specified, and must be if <gens>
# is empty (in which case M will be empty as well).
DeclareGlobalFunction("LeftQuasigroup");
DeclareGlobalFunction("RightQuasigroup");
DeclareGlobalFunction("LeftRack");
DeclareGlobalFunction("RightRack");
DeclareGlobalFunction("LeftQuandle");
DeclareGlobalFunction("RightQuandle");

# Underlying operation
DeclareGlobalFunction("CloneOfTypeByGenerators");

# Attributes for the generators

# Generates the structure by \* and LeftQuotient. Note that for finite
# structures, these are the same as the GeneratorsOfMagma but in general more
# elements might be required to generate the structure just under *
DeclareAttribute("GeneratorsOfLeftQuasigroup", IsLeftQuasigroup);
InstallImmediateMethod(GeneratorsOfMagma,
  "finite left quasigroups *-generated by left quasigroup generators",
  IsLeftQuasigroup and IsFinite,
  1,
  q -> GeneratorsOfLeftQuasigroup(q)
);

# Generates the structure by \* and \/, same considerations as above
DeclareAttribute("GeneratorsOfRightQuasigroup", IsRightQuasigroup);
InstallImmediateMethod(GeneratorsOfMagma,
  "finite right quasigroups *-generated by right quasigroup generators",
  IsRightQuasigroup and IsFinite,
  2,
  q -> GeneratorsOfRightQuasigroup(q)
);