README.md | enso.nim: attempt added for safer Exception handling, README updated to reflect current state and philosophy

src/enso.nim

@@ -3,11 +3,13 @@ import std/[options, os, sugar]
 # Declarations
 
 type
-  Error* = enum OK, ERR
   IO*[T] = proc(): T
+  Unit*  = object
 
+func attempt*[T](uf: IO[T]): Option[T]
+func attempt*(uf: IO[void]): Option[Unit]
 func fileread*(file: string): IO[Option[string]]
-func filewrite*(data: string, file: string): IO[Error]
+func filewrite*(data: string, file: string): IO[Option[Unit]]
 func flatmap*[T, U](io: IO[T], fn: T -> IO[U]): IO[U]
 func lift*(fn: proc(): void): IO[void]
 func lift*[T](fn: proc(): T): IO[T]
@@ -20,31 +22,35 @@ func to_IO*[T](val: T): IO[T]
 
 # Unsafe
 
-proc read_unsafe(file: string): Option[string] =
+proc unsafe[T](uf: IO[T]): Option[T] =
   try:
-    let data: string = readFile(file)
-    some(data)
-  except IOError:
-    none(string)
+    let sf: T = uf()
+    some(sf)
+  except:
+    none(T)
 
-proc write_unsafe(data: string, file: string): Error =
+proc unsafe(uf: IO[void]): Option[Unit] =
   try:
-    writeFile(file, data)
-    OK
-  except IOError:
-    ERR
+    run uf
+    some(Unit())
+  except:
+    none(Unit)
 
 # Definitions
 
+func attempt*[T](uf: IO[T]): Option[T] = unsafe(uf)
+
+func attempt*(uf: IO[void]): Option[Unit] = unsafe(uf)
+
 func fileread*(file: string): IO[Option[string]] =
   proc(): Option[string] =
     if fileExists(file):
-      read_unsafe(file)
+      attempt(lift () => readFile(file))
     else:
       none(string)
 
-func filewrite*(data: string, file: string): IO[Error] =
-  proc(): Error = write_unsafe(data, file)
+func filewrite*(data: string, file: string): IO[Option[Unit]] =
+  proc(): Option[Unit] = attempt(lift () => writeFile(file, data))
 
 func flatmap*[T, U](io: IO[T], fn: T -> IO[U]): IO[U] = join(map(io, fn))