Core.hs

{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE Strict #-}
{-# LANGUAGE StrictData #-}
-- | This module contains very basic definitions for Futhark - so basic,
-- that they can be shared between the internal and external
-- representation.
module Language.Futhark.Core
  ( Uniqueness(..)
  , StreamOrd(..)
  , Commutativity(..)

  -- * Location utilities
  , locStr
  , locStrRel
  , prettyStacktrace

  -- * Name handling
  , Name
  , nameToString
  , nameFromString
  , nameToText
  , nameFromText
  , VName(..)
  , baseTag
  , baseName
  , baseString
  , pretty
  , quote
  , pquote

  -- * Special identifiers
  , defaultEntryPoint

    -- * Integer re-export
  , Int8, Int16, Int32, Int64
  , Word8, Word16, Word32, Word64
  )

where

import Data.Int (Int8, Int16, Int32, Int64)
import Data.String
import Data.Word (Word8, Word16, Word32, Word64)
import Data.Loc
import qualified Data.Text as T

import Futhark.Util.Pretty

-- | The uniqueness attribute of a type.  This essentially indicates
-- whether or not in-place modifications are acceptable.  With respect
-- to ordering, 'Unique' is greater than 'Nonunique'.
data Uniqueness = Nonunique -- ^ May have references outside current function.
                | Unique    -- ^ No references outside current function.
                  deriving (Eq, Ord, Show)

instance Semigroup Uniqueness where
  (<>) = min

instance Monoid Uniqueness where
  mempty = Unique

instance Pretty Uniqueness where
  ppr Unique = star
  ppr Nonunique = empty

data StreamOrd  = InOrder
                | Disorder
                    deriving (Eq, Ord, Show)

-- | Whether some operator is commutative or not.  The 'Monoid'
-- instance returns the least commutative of its arguments.
data Commutativity = Noncommutative
                   | Commutative
                     deriving (Eq, Ord, Show)

instance Semigroup Commutativity where
  (<>) = min

instance Monoid Commutativity where
  mempty = Commutative

-- | The name of the default program entry point (main).
defaultEntryPoint :: Name
defaultEntryPoint = nameFromString "main"

-- | The abstract (not really) type representing names in the Futhark
-- compiler.  'String's, being lists of characters, are very slow,
-- while 'T.Text's are based on byte-arrays.
newtype Name = Name T.Text
  deriving (Show, Eq, Ord, IsString, Semigroup)

instance Pretty Name where
  ppr = text . nameToString

-- | Convert a name to the corresponding list of characters.
nameToString :: Name -> String
nameToString (Name t) = T.unpack t

-- | Convert a list of characters to the corresponding name.
nameFromString :: String -> Name
nameFromString = Name . T.pack

-- | Convert a name to the corresponding 'T.Text'.
nameToText :: Name -> T.Text
nameToText (Name t) = t

-- | Convert a 'T.Text' to the corresponding name.
nameFromText :: T.Text -> Name
nameFromText = Name

-- | A human-readable location string, of the form
-- @filename:lineno:columnno@.  This follows the GNU coding standards
-- for error messages:
-- https://www.gnu.org/prep/standards/html_node/Errors.html
--
-- This function assumes that both start and end position is in the
-- same file (it is not clear what the alternative would even mean).
locStr :: Located a => a -> String
locStr a =
  case locOf a of
    NoLoc -> "unknown location"
    Loc (Pos file line1 col1 _) (Pos _ line2 col2 _)
    -- Do not show line2 if it is identical to line1.
      | line1 == line2 ->
          first_part ++ "-" ++ show col2
      | otherwise ->
          first_part ++ "-" ++ show line2 ++ ":" ++ show col2
      where first_part = file ++ ":" ++ show line1 ++ ":" ++ show col1


-- | Like 'locStr', but @locStrRel prev now@ prints the location @now@
-- with the file name left out if the same as @prev@.  This is useful
-- when printing messages that are all in the context of some
-- initially printed location (e.g. the first mention contains the
-- file name; the rest just line and column name).
locStrRel :: (Located a, Located b) => a -> b -> String
locStrRel a b =
  case (locOf a, locOf b) of
    (Loc (Pos a_file _ _ _) _, Loc (Pos b_file line1 col1 _) (Pos _ line2 col2 _))
      | a_file == b_file,
        line1 == line2 ->
          first_part ++ "-" ++ show col2
      | a_file == b_file ->
          first_part ++ "-" ++ show line2 ++ ":" ++ show col2
      where first_part = show line1 ++ ":" ++ show col1
    _ -> locStr b

-- | Given a list of strings representing entries in the stack trace
-- and the index of the frame to highlight, produce a final
-- newline-terminated string for showing to the user.  This string
-- should also be preceded by a newline.  The most recent stack frame
-- must come first in the list.
prettyStacktrace :: Int -> [String] -> String
prettyStacktrace cur = unlines . zipWith f [(0::Int)..]
  where -- Formatting hack: assume no stack is deeper than 100
        -- elements.  Since Futhark does not support recursion, going
        -- beyond that would require a truly perverse program.
        f i x = (if cur == i then "-> " else "   ") ++
                '#' : show i ++
                (if i > 9 then "" else " ") ++ " " ++ x

-- | A name tagged with some integer.  Only the integer is used in
-- comparisons, no matter the type of @vn@.
data VName = VName !Name !Int
  deriving (Show)

-- | Return the tag contained in the 'VName'.
baseTag :: VName -> Int
baseTag (VName _ tag) = tag

-- | Return the name contained in the 'VName'.
baseName :: VName -> Name
baseName (VName vn _) = vn

-- | Return the base 'Name' converted to a string.
baseString :: VName -> String
baseString = nameToString . baseName

instance Eq VName where
  VName _ x == VName _ y = x == y

instance Ord VName where
  VName _ x `compare` VName _ y = x `compare` y

-- | Enclose a string in the prefered quotes used in error messages.
-- These are picked to not collide with characters permitted in
-- identifiers.
quote :: String -> String
quote s = "\"" ++ s ++ "\""

-- | As 'quote', but works on prettyprinted representation.
pquote :: Doc -> Doc
pquote = dquotes