diff options
Diffstat (limited to 'src/Parser.hs')
| -rw-r--r-- | src/Parser.hs | 23 |
1 files changed, 19 insertions, 4 deletions
diff --git a/src/Parser.hs b/src/Parser.hs index 679f318..508be0f 100644 --- a/src/Parser.hs +++ b/src/Parser.hs @@ -10,6 +10,8 @@ import qualified Data.Text as T import LTypes import Utils +-- | Convert a string into an 'LWord'. +parseWord :: String -> LWord parseWord rawStr | isIntStr rawStr = LInteger (read rawStr) | isFloatStr rawStr = LFloat $ read rawStr @@ -18,9 +20,13 @@ parseWord rawStr | "$" `isPrefixOf` rawStr = LLabel $ tail rawStr | otherwise = LSymbol rawStr +-- | Remove line suffixes starting with the comment marker '--'. +removeComments :: String -> String removeComments = lines .> map (T.pack .> T.splitOn (T.pack "--") .> head .> T.unpack) .> unlines +-- | Preprocess the source by inserting "string literal references" in place of +-- string literals (e.g. "hello world") in order to remove significant whitespace from the source. processStringLiterals :: Maybe String -> Map String [LWord] -> String -> ExceptT LException IO (String, Map String [LWord]) processStringLiterals currentM refMap [] = case currentM of Just _ -> throwError $ LException "nonterminated string literal" @@ -46,8 +52,14 @@ processStringLiterals currentM refMap (c : source) = case c of -- proceed normally processStringLiterals Nothing refMap source $> fmap (B.first (c :)) -internalNVar n = LLabel $ fmt "$__%%" [show n] +-- | Format a new internal variable 'LLabel' for use in string literal desugaring. +produceInternalNVar :: Int -> LWord +produceInternalNVar n = LLabel $ fmt "$__%%" [show n] +-- | Desugar a "string phrase" (i.e. phrase containing only chars). +-- If the string contains the substring '%%', construct a sequence of words that consumes another string +-- phrase from the stack when evaluated, inserting that string where the '%%' substring was located. Can be used +-- with N instances of the '%%' substring (consumes N strings from stack). processSLInterpolations :: LWord -> ExceptT LException IO [LWord] processSLInterpolations strP@(LPhrase lChars) | "%%" `isInfixOf` chars = pure [LPhrase interpolated, LSymbol "unphrase"] @@ -58,18 +70,21 @@ processSLInterpolations strP@(LPhrase lChars) separatedByMarker = T.pack chars $> T.splitOn (T.pack "%%") .> map (T.unpack .> map LChar) labelIndices = [0 .. length separatedByMarker - 1 - 1] -- store n - 1 variables from stack - varStores = labelIndices $> map (\n -> [internalNVar n, LSymbol "!"]) .> reverse + varStores = labelIndices $> map (\n -> [produceInternalNVar n, LSymbol "!"]) .> reverse part1 = concat varStores -- interleave the n substrings and n - 1 variable reads - symbolLookups = labelIndices $> map (\n -> [internalNVar n, LSymbol "@", LSymbol "unphrase"]) + symbolLookups = labelIndices $> map (\n -> [produceInternalNVar n, LSymbol "@", LSymbol "unphrase"]) part2 = LSymbol "'[" : concat (mix separatedByMarker symbolLookups) ++ [LSymbol "']", LSymbol "phrase"] -- forget the temp variables used - varForgets = labelIndices $> map (\n -> [internalNVar n, LSymbol "forget"]) + varForgets = labelIndices $> map (\n -> [produceInternalNVar n, LSymbol "forget"]) part3 = concat varForgets -- combine everything into one phrase interpolated = part1 ++ part2 ++ part3 processSLInterpolations p = throwError $ LException $ fmt "non-phrase in processSLInterpolations: %%" [show p] +-- | Parse source code string to a list of 'LWord's and a string literal refmap (see 'LTypes.LState' for explanation). +-- Throws exception on parsing error. +parseSource :: String -> ExceptT LException IO ([LWord], Map String [LWord]) parseSource source = do let woComments = source $> removeComments (woStringLiterals, stringLiteralRefMap) <- processStringLiterals Nothing M.empty woComments |