(pgf2) Readme, license, changelog

src/runtime/haskell-bind/README.md

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+# PGF2
+
+This is a Haskell binding to the PGF runtime in C.
+
+The exposed modules are:
+
+- `PGF2`: a user API similar to Python and Java APIs
+- `PGF2.Internal`: an internal module with FFI definitions for the relevant C functions
+
+## How to compile
+
+```
+cabal install
+```
+
+**Note:** you must have the PGF C runtime already installed and available.
+See <https://github.com/GrammaticalFramework/gf-core/blob/master/src/runtime/c/INSTALL>
+
+## How to use
+
+Import PGF to the Haskell program that you're writing. 
+The Cabal infrastructure will make sure to tell the compiler
+where to find the relevant modules.
+
+## Example
+
+```haskell
+module Main where
+
+import PGF2
+import qualified Data.Map as Map
+
+main = do
+  pgf <- readPGF "App12.pgf"
+  let Just eng = Map.lookup "AppEng" (languages pgf)
+  
+  -- Parsing
+  let res = parse eng (startCat pgf) "this is a small theatre"
+  let ParseOk ((tree,prob):rest) = res
+  print tree
+  
+  -- Linearisation
+  let Just expr = readExpr "AdjCN (PositA red_A) (UseN theatre_N)"
+  let s = linearize eng expr
+  print s
+```