=====Right hoops===== ====Definition==== A \emph{right hoop} is a structure $\mathbf{A}=\langle A,\cdot,/,1\rangle $ of type $\langle 2,2,0\rangle$ such that $\langle A,\cdot ,1\rangle $ is a [[monoid]] $x/(y\cdot z) = (x/z)/y$ $x/x=1$ $(x/y)\cdot y = (y/x)\cdot x$ Remark: This definition shows that right hoops form a variety. Right hoops are partially ordered by the relation $x\leq y \iff y/x=1$. The operation $x\wedge y = (x/y)\cdot y$ is a meet with respect to this order. ====Definition==== A \emph{right hoop} is a structure $\mathbf{A}=\langle A,\cdot,/,1\rangle $ of type $\langle 2,2,0\rangle$ such that $x\cdot y = y\cdot x$ $x\cdot 1 = x$ $x/(y\cdot z) = (x/z)/y$ $x/x=1$ $(x/y)\cdot y = (y/x)\cdot x$ ====Definition==== A \emph{right hoop} is a structure $\mathbf{A}=\langle A,\cdot,/,1\rangle $ of type $\langle 2,2,0\rangle$ such that $\langle A,\cdot ,1\rangle $ is a [[commutative monoid]] and if $x\le y$ is defined by $y/x = 1$ then $\le$ is a partial order, $/$ is the right residual of $\cdot$, i.e., $\ x\cdot y\le z \iff x\le z/y$, and $(x/y)\cdot y = (y/x)\cdot x$. ==Morphisms== Let $\mathbf{A}$ and $\mathbf{B}$ be hoops. A morphism from $\mathbf{A}$ to $\mathbf{B}$ is a function $h:A\rightarrow B$ that is a homomorphism: $h(x\cdot y)=h(x)\cdot h(y)$, $h(x/y)=h(x)/h(y) $, $h(1)=1$ ====Examples==== Example 1: ====Basic results==== ====Properties==== ^[[Classtype]] |variety | ^[[Equational theory]] | | ^[[Quasiequational theory]] | | ^[[First-order theory]] | | ^[[Locally finite]] |no | ^[[Residual size]] |unbounded | ^[[Congruence distributive]] | | ^[[Congruence modular]] | | ^[[Congruence n-permutable]] | | ^[[Congruence regular]] | | ^[[Congruence uniform]] | | ^[[Congruence extension property]] | | ^[[Definable principal congruences]] | | ^[[Equationally def. pr. cong.]] | | ^[[Amalgamation property]] | | ^[[Strong amalgamation property]] | | ^[[Epimorphisms are surjective]] | | ====Finite members==== $\begin{array}{lr} f(1)= &1\\ f(2)= &1\\ f(3)= &2\\ f(4)= &8\\ f(5)= &24\\ f(6)= &91\\ f(7)= &\\ \end{array}$ ====Subclasses==== [[hoops]] ====Superclasses==== [[Porrims]] ====References==== [(Ln19xx> )]