Semantic Analysis - Crafting a Compiler - page 367

function gather L abels (CaseItem cn ) returns intList

if null

then return (

cn . more =

gather L abels ( cn . labelList ))

else

rest ← gather L abels ( cn . more )

return ( append ( gather L abels ( cn . labelList ) , rest ))

end

function gather L abels ( LabelList lln ) returns intList

if null

then return ( null )
else

lln =

rest ← gather L abels ( llnn . more )

if lln . caseLabel = null

then return ( rest )
else return ( cons ( lln . caseLabel , rest ))

end

procedure check F or D uplicates ( intList il )

if length ( il ) > 1

then
if head ( il ) = head ( tail ( il ))

then
call error (” Duplicatecaselabel :” ,head ( il ))

else
call check F or D uplicates ( tail ( il ))

end

function count D efaults (CaseItem cn ) returns int

if null

then return (0)
else return (

cn =

count D efaults ( cn . labelList ) +count D efaults ( cn . more ))

end

function count D efaults ( LabelList lln ) returns int

if null

then return (0)
if lln . isDe f ault
then return ( 1

lln =

( lln . more ) )

+count D efaults

else
return ( count D efaults ( lln . more ))

end

Figure 9.22: Utility Semantic Methods for Switch Statements