diff -r fc7841f31388 -r 813fabceec00 doc-src/AxClass/Group/Product.thy --- a/doc-src/AxClass/Group/Product.thy Mon May 22 10:31:44 2000 +0200 +++ b/doc-src/AxClass/Group/Product.thy Mon May 22 11:56:55 2000 +0200 @@ -5,14 +5,14 @@ text {* \medskip\noindent There is still a feature of Isabelle's type system - left that we have not yet used: when declaring polymorphic constants - $c :: \sigma$, the type variables occurring in $\sigma$ may be - constrained by type classes (or even general sorts) in an arbitrary - way. Note that by default, in Isabelle/HOL the declaration $\TIMES - :: \alpha \To \alpha \To \alpha$ is actually an abbreviation for - $\TIMES :: (\alpha::term) \To \alpha \To \alpha$. Since class $term$ - is the universal class of HOL, this is not really a restriction at - all. + left that we have not yet discussed. When declaring polymorphic + constants $c :: \sigma$, the type variables occurring in $\sigma$ may + be constrained by type classes (or even general sorts) in an + arbitrary way. Note that by default, in Isabelle/HOL the declaration + $\TIMES :: \alpha \To \alpha \To \alpha$ is actually an abbreviation + for $\TIMES :: (\alpha::term) \To \alpha \To \alpha$. Since class + $term$ is the universal class of HOL, this is not really a constraint + at all. The $product$ class below provides a less degenerate example of syntactic type classes. @@ -21,7 +21,7 @@ axclass product < "term"; consts - product :: "'a::product \\ 'a \\ 'a" (infixl "\\" 70); + product :: "'a::product \\ 'a \\ 'a" (infixl "\\" 70); text {* Here class $product$ is defined as subclass of $term$ without any @@ -55,7 +55,7 @@ instance bool :: product; by intro_classes; defs - product_bool_def: "x \\ y \\ x \\ y"; + product_bool_def: "x \\ y \\ x \\ y"; text {* The definition $prod_bool_def$ becomes syntactically well-formed only @@ -70,14 +70,14 @@ \medskip While Isabelle type classes and those of Haskell are almost the same as far as type-checking and type inference are concerned, - there are major semantic differences. Haskell classes require their - instances to \emph{provide operations} of certain \emph{names}. + there are important semantic differences. Haskell classes require + their instances to \emph{provide operations} of certain \emph{names}. Therefore, its \texttt{instance} has a \texttt{where} part that tells the system what these ``member functions'' should be. - This style of \texttt{instance} won't make much sense in Isabelle, - because its meta-logic has no corresponding notion of ``providing - operations'' or ``names''. + This style of \texttt{instance} won't make much sense in Isabelle's + meta-logic, because there is no internal notion of ``providing + operations'' or even ``names of functions''. *}; end; \ No newline at end of file