Add Nat.fromText

CONTRIBUTORS.markdown

@@ -22,3 +22,4 @@ The format for this list: name, GitHub handle, and then optional blurb about wha
 * Scott Christopher (@scott-christopher)
 * Alex Zolotko (@azolotko)
 * Ian Denhardt (@zenhack)
+* Mitchell Rosen (@mitchellwrosen)

parser-typechecker/src/Unison/Builtin.hs

@@ -241,6 +241,7 @@ builtinsSrc =
   , B "Nat.isOdd" $ nat --> boolean
   , B "Nat.toInt" $ nat --> int
   , B "Nat.toText" $ nat --> text
+  , B "Nat.fromText" $ text --> optional nat
 
   , B "Float.+" $ float --> float --> float
   , B "Float.-" $ float --> float --> float

parser-typechecker/src/Unison/Runtime/Rt1.hs

@@ -331,6 +331,8 @@ builtinCompilationEnv = CompilationEnv (builtinsMap <> IR.builtins) mempty
     , mk1 "Float.truncate"      atf (pure . I) truncate
 
     , mk1 "Nat.toText" atn (pure . T) (Text.pack . show)
+    , mk1 "Nat.fromText" att (pure . IR.maybeToOptional . fmap N) (
+        (\x -> readMaybe x :: Maybe Word64) . Text.unpack)
 
     -- Float Utils
     , mk1 "Float.abs"           atf (pure . F) abs

parser-typechecker/unison-parser-typechecker.cabal

@@ -185,7 +185,7 @@ library
     io-streams,
     lens,
     ListLike,
-    megaparsec,
+    megaparsec >= 5.0.0 && < 7.0.0,
     memory,
     mmorph,
     monad-loops,