Re: static constants -- ideas?

Don Stewart dons@galois.com:

jay:

...

Don Stewart dons@galois.com:

...

jay:

...

I also have constants that are too large to compile. I am resigned to loading them from data files--other solutions seem even worse. ... Data.Binary eases the irritation somewhat.

Did you try bytestring literals (and maybe parsing them in-memory with Data.Binary)?

That didn't occur to me, since neither of my large constants includes strings.... I think you're suggesting that each constant could appear in the source as a long bytestring and be deserialized into the data structure. If that works, it should improve the startup time, but it's still not as nice as simply compiling it straight up.

I'll try it.

Here's an example, which stores a Data.Map in a gzip-compressed bytestring literal (a C string literal in the compiled code). The Map is reconstructed on startup.

{-# LANGUAGE OverloadedStrings #-}

import Data.Binary import qualified Data.Map as M import qualified Data.ByteString.Char8 as S import Data.ByteString.Lazy import Codec.Compression.GZip

-- -- this is a gzip compressed literal bytestring, storing a binary- encoded Data.Map -- mytable = "\US\139\b\NUL\NUL\NUL\NUL\NUL\NUL\ETXEN\219\SO\194 \f\197\224 \188\196\CAN\227\US\224\171~\NAKc\GS4ce\161`\178\191\215(\176\190\180\167 \231\210\n\241\171\203\191\ti\157\217\149\249< \ENQ\214\&9>\202\162\179a \132X\233\ESC=\231\215\164\SYN\157\DC2D\226*\146\174o\t\167\DLE\209\"i_ \240\193\129\199

main = print =<< M.lookup "ghc" m where -- build the table from the bytestring: m :: M.Map String (Maybe String) m = decode . decompress . fromChunks . return $ mytable

Running it:

$ ./A Just "dinosaur!"

:)

Important to use a bytestring, since that gets compiled to a C string literal (and not messed with by the simplifier).

-- Don