function to read bril from text file

bril-sources/add.json

@@ -0,0 +1,36 @@
+"functions": [
+    {
+      "instrs": [
+        {
+          "dest": "v0",
+          "op": "const",
+          "type": "int",
+          "value": 1
+        },
+        {
+          "dest": "v1",
+          "op": "const",
+          "type": "int",
+          "value": 2
+        },
+        {
+          "args": [
+            "v0",
+            "v1"
+          ],
+          "dest": "v2",
+          "op": "add",
+          "type": "int"
+        },
+        {
+          "args": [
+            "v2"
+          ],
+          "op": "print"
+        }
+      ],
+      "name": "main"
+    }
+  ]
+}
+

eoc.cabal

@@ -23,7 +23,8 @@ library eoc-lib
         base >=4.13 && <4.18,
         text >= 2.0,
         aeson >= 2.2,
-        sorted-list ^>= 0.2
+        sorted-list ^>= 0.2,
+        bytestring >= 0.11
     default-language: Haskell2010
   default-extensions: DeriveGeneric, OverloadedStrings
 

lib/Bril.hs

@@ -2,9 +2,10 @@ module Bril (
     Function (..), Type (..), Value (..), InstrOperation (..), FunctionArg (..), Program (..),
     Instruction (..),
     parseValue,
+    parseBrilFromPath, parseBrilJSON,
     )where
 
-import Data.Aeson (FromJSON, parseJSON, withObject, withText, (.:), (.:?), decode)
+import Data.Aeson (FromJSON, parseJSON, withObject, withText, (.:), (.:?), eitherDecode)
 import Data.Aeson.Types (Parser, modifyFailure)
 import qualified Data.Aeson (Value, Object, Key)
 import Data.Aeson.KeyMap
@@ -14,6 +15,7 @@ import Data.Text.Read (Reader, signed, decimal)
 import Data.SortedList
 import Data.Maybe (fromMaybe, isJust)
 
+import qualified Data.ByteString.Lazy as LB
 
 data Program = Program { programFns :: [Function] }
     deriving (Show, Eq)
@@ -215,4 +217,8 @@ parseValue Int =
                     else fail $ "invalid int literal: " ++ (T.unpack v)
             
 
-parseBrilJSON text = (decode text :: Maybe Program)
+parseBrilJSON text = (eitherDecode text :: Either String Program)
+
+parseBrilFromPath path = do
+    contents <- LB.readFile path
+    return $ parseBrilJSON contents