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| -rw-r--r-- | ghc/docs/users_guide/glasgow_exts.sgml | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/ghc/docs/users_guide/glasgow_exts.sgml b/ghc/docs/users_guide/glasgow_exts.sgml index 7cb23c0520..b52adc9148 100644 --- a/ghc/docs/users_guide/glasgow_exts.sgml +++ b/ghc/docs/users_guide/glasgow_exts.sgml @@ -4279,6 +4279,22 @@ That is, just leave off the "where" clasuse. Of course, you can put in the where clause and over-ride whichever methods you please. +<Sect2> <Title> Using generics </Title> +</Sect2> +<Para> +To use generics you need to +<ItemizedList> +<ListItem> +Use the <Option>-fgenerics</Option> flag. +</ListItem> +<ListItem> +Import the module <Literal>Generics</Literal> from the <Literal>lang</Literal> package. +This import brings into scope the data types <Literal>Unit</Literal>, <Literal>:*:</Literal>, +and <Literal>:+:</Literal>. (You don't need this import if you don't mention these +types explicitly; for example, if you are simply giving instance declarations.) +</ListItem> +</ItemizedList> + <Sect2> <Title> Changes wrt the paper </Title> <Para> Note that the type constructors <Literal>:+:</Literal> and <Literal>:*:</Literal> |