finish solved examples for chapter 7

sofp-src/sofp-typeclasses.lyx

@@ -22344,12 +22344,49 @@ Can we recognize a pointed contrafunctor
  by looking at its type expression, e.g.
 \begin_inset Formula 
 \[
-C^{A,B}\triangleq\left(\bbnum 1+A\Rightarrow\text{Int}\right)+(\text{String}\times A\times A\Rightarrow\text{String})\quad?
+C^{A}\triangleq\left(\bbnum 1+A\Rightarrow\text{Int}\right)+(\text{String}\times A\times A\Rightarrow\text{String})\quad?
 \]
 
 \end_inset
 
-We ***
+We need to set the type parameter to 
+\begin_inset Formula $\bbnum 1$
+\end_inset
+
+ and try to create a value of type 
+\begin_inset Formula $C^{\bbnum 1}$
+\end_inset
+
+.
+ For this example:
+\begin_inset Formula 
+\[
+C^{\bbnum 1}=\left(\bbnum 1+\bbnum 1\Rightarrow\text{Int}\right)+(\text{String}\times\bbnum 1\times\bbnum 1\Rightarrow\text{String})\quad.
+\]
+
+\end_inset
+
+We can certainly create values of this type, e.g.
+\begin_inset space ~
+\end_inset
+
+a constant function returning an integer 
+\begin_inset Formula $123$
+\end_inset
+
+:
+\begin_inset Formula 
+\[
+\text{wu}_{C}\triangleq(\_^{:\bbnum 1+\bbnum 1}\Rightarrow123)+\bbnum 0\quad.
+\]
+
+\end_inset
+
+So, the contrafunctor 
+\begin_inset Formula $C$
+\end_inset
+
+ is pointed.
 \end_layout
 
 \begin_layout Section