enso.nim: Added file operations

src/enso.nim

@@ -1,11 +1,14 @@
-import std/sugar
+import std/[options, os, sugar]
 
 # Declarations
 
 type
+  Error*    = enum OK, ERR
   FileDesc* = enum STDIN, STDOUT, STDERR
   IO*[T]    = proc(): T
 
+func fileread*(file: string): IO[Option[string]]
+func filewrite*(data: string, file: string): IO[Error]
 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]
@@ -16,8 +19,34 @@ func run*[T](io: IO[T]): T
 func strput*(str: string): IO[void]
 func to_IO*[T](val: T): IO[T]
 
+# Unsafe
+
+proc read_unsafe(file: string): Option[string] =
+  try:
+    let data: string = readFile(file)
+    some(data)
+  except IOError:
+    none(string)
+
+proc write_unsafe(data: string, file: string): Error =
+  try:
+    writeFile(file, data)
+    OK
+  except IOError:
+    ERR
+
 # Definitions
 
+func fileread*(file: string): IO[Option[string]] =
+  proc(): Option[string] =
+    if fileExists(file):
+      read_unsafe(file)
+    else:
+      none(string)
+
+func filewrite*(data: string, file: string): IO[Error] =
+  proc(): Error = write_unsafe(data, file)
+
 func flatmap*[T, U](io: IO[T], fn: T -> IO[U]): IO[U] = join(map(io, fn))
 
 func lift*(fn: proc(): void): IO[void] =

tests/test.nim

@@ -1,5 +1,5 @@
 import enso
-import std/[os, strformat, sugar]
+import std/[options, strformat, sugar]
 
 proc unsafe_void(str: string) =
   echo str
@@ -8,13 +8,6 @@ proc unsafe_int(str: string): int =
   echo str
   result = 1
 
-func check_file(name: string): IO[string] =
-  proc(): string =
-    if fileExists(name):
-      result = readFile(name)
-    else:
-      result = "Not found"
-
 func main() =
   run strput("Hello from Enso!")
 
@@ -32,13 +25,29 @@ func main() =
       name()
 
   let
-    nested: IO[IO[string]] = get_filename.map(check_file)
-    joined: IO[string]     = nested.join
+    nested:   IO[IO[Option[string]]] = get_filename.map(fileread)
+    joined:   IO[Option[string]]     = nested.join
+    join_opt: Option[string]         = joined()
 
-  run strput(joined())
+  if join_opt.isSome:
+    run strput(join_opt.get)
+  else:
+    run strput("joined had no data")
 
-  let flat: IO[string] = get_filename.flatmap(check_file)
-  run strput(flat())
+  let
+    flat:     IO[Option[string]] = get_filename.flatmap(fileread)
+    flat_opt: Option[string]     = flat()
+
+  if flat_opt.isSome:
+    run strput(flat_opt.get)
+  else:
+    run strput("flat had no data")
+
+  let writer: Error = run filewrite("Hello world!\n", "test.txt")
+  if writer == OK:
+    run strput("Successfully wrote test.txt!")
+  else:
+    run strput("Could not write test.txt!")
 
 when isMainModule:
   main()