Preorder

$\textbf{Above} \; A \; R \; S \; y$

---

$\textbf{Preorder} \; A \; R$

$\textbf{Includes} \; S \; A$

$y \in S$

$\forall(s : s \in S : R.s.y)$

---

Notation.

1. $\textbf{Above} \; S \; y$ abbreviates $\textbf{Above} \; A \; R \; S \; y$ when $A$ and $R$ are clear from the context.

2. $\textbf{Above} \; S \; y$ is abbreviated by $S \sqsubseteq y$.

---

pred Above(A: set univ, R: univ->univ, S: set univ, y: univ) {
  Preorder[A,R]
  S in A
  y in A
  all s: univ | s in S implies s->y in R 
}

$\textbf{Above} \; A \; R \; S := \{ \; y : \textbf{Above} \; A \; R \; S \; y \; \}$

---

fun Above(A: set univ, R: univ->univ, S: set univ) : set univ {
  { y: univ | Above[A,R,S,y] }
}

$\textbf{Below} \; A \; R \; S \; y$

---

$\textbf{Preorder} \; A \; R$

$\textbf{Includes} \; S \; A$

$y \in A$

$\forall(s : s \in S : R.y.s)$

---

Notation.

1. $\textbf{Below} \; S \; y$ abbreviates $\textbf{Below} \; A \; R \; S \; y$ when $A$ and $R$ are clear from the context.

2. $\textbf{Below} \; S \; y$ is abbreviated by $S \sqsupseteq y$.

---

pred Below(A: set univ, R: univ->univ, S: set univ, y: univ) {
  Preorder[A,R]
  S in A
  y in A
  all s: univ | s in S implies y->s in R 
}

$\textbf{Below} \; A \; R \; S := \{ \; y : \textbf{Below} \; A \; R \; S \; y \; \}$

---

fun Below(A: set univ, R: univ->univ, S: set univ) : set univ {
  { y: univ | Below[A,R,S,y] }
}

$\textbf{Equivalent} \; A \; R \; x \; y$

---

$\textbf{Preorder} \; A \; R$

$x \in A$

$y \in A$

$R.x.y \wedge R.y.x$

---

Notation.

1. $\textbf{Equivalent} \; x \; y$ abbreviates $\textbf{Equivalent} \; A \; R \; x \; y$ when $A$ and $R$ are clear from the context.

2. $\textbf{Equivalent} \; x \; y$ is abbreviated by $x \cong y$.

---

pred Equivalent(A: set univ, R: univ->univ, x,y: univ) {
  Preorder[A,R]
  x in A
  y in A
  x->y in R and y->x in R
}

$\textbf{Opposite} \; A \; R := \{ x,y \in A : R.x.y : \textbf{pair} \; y \; x \}$

---

$\textbf{Preorder} \; A \; R$

$\textbf{Product} \; A \; B \; R \; S := \{ \; p,q \in A \times B : R.(\textbf{fst}.p).(\textbf{fst}.q) \wedge S.(\textbf{snd}.p).(\textbf{snd}.q) : \textbf{pair} \; p \; q \; \}$

---

$\textbf{Preorder} \; A \; R$

$\textbf{Preorder} \; B \; S$

---

Notation.

1. $\textbf{Product} \; R \; S$ abbreviates $\textbf{Product} \; A \; B \; R \; S$ when $A$ and $B$ are clear from the context.

2. $\textbf{Product} \; R \; S$ can be written $R \times S$.