Commit a4a66440 authored by Björn Peemöller 's avatar Björn Peemöller
Browse files

First working version of fcase expressions

parent a6d58b10
......@@ -288,7 +288,9 @@ uses flexible matching.
> trEquation vs vs' (Equation _ (FunLhs _ ts) rhs) = do
> -- construct renaming of variables inside constructor terms
> let patternRenaming = foldr2 bindRenameEnv Map.empty vs ts
> -- translate right-hand-side
> rhs' <- trRhs vs' patternRenaming rhs
> -- convert patterns
> return (zipWith trPattern vs ts, rhs')
> trEquation _ _ _
> = internalError "Translation of non-FunLhs euqation not defined"
......@@ -350,9 +352,9 @@ instance, if one of the alternatives contains an \texttt{@}-pattern.
> trExpr (v:vs) env (Case r ct e alts) = do
> -- the ident v is used for the case expression subject, as this could
> -- be referenced in the case alternatives by a variable pattern
> e' <- trExpr vs env e
> e' <- trExpr vs env e
> let matcher = if ct == Flex then flexMatch else rigidMatch
> expr <- matcher r [v] `liftM` mapM (trAlt vs env) alts
> expr <- matcher r [v] `liftM` mapM (trAlt (v:vs) env) alts
> return $ case expr of
> IL.Case r' mode (IL.Variable v') alts'
> -- subject is not referenced -> forget v and insert subject
......@@ -425,16 +427,19 @@ hand sides of the remaining rules, eventually combining them using
Actually, the algorithm below combines the search for inductive and
demanded positions. The function \texttt{flexMatch} scans the argument
lists for the left-most demanded position. If this turns out to be
also an inductive position, the function \texttt{matchInductive} is
also an inductive position, the function \texttt{flexMatchInductive} is
called in order to generate a \texttt{case} expression. Otherwise, the
function \texttt{optFlexMatch} is called that tries to find an inductive
position in the remaining arguments. If one is found,
\texttt{matchInductive} is called, otherwise the function
\texttt{flexMatchInductive} is called, otherwise the function
\texttt{optFlexMatch} uses the demanded argument position found by
\texttt{match}.
\texttt{flexMatch}.
\begin{verbatim}
> -- a 'Match' is a list of patterns and the respective expression
> type Match = ([NestedTerm], IL.Expression)
> -- a 'Match'' is a 'Match' with deferred patterns to be matched after
> -- the next inductive position
> type Match' = ([NestedTerm] -> [NestedTerm], [NestedTerm], IL.Expression)
> flexMatch :: SrcRef -- source reference
......
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