enso.nim: Next time don't get confused

src/enso.nim

@@ -10,7 +10,7 @@ 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]
 func join*[T](io: IO[IO[T]]): IO[T]
-func map*[T, U](io: IO[seq[T]], fn: T -> U): IO[seq[U]]
+func map*[T, U](io: IO[T], fn: T -> U): IO[U]
 func readstr*(stream: FileDesc): IO[string]
 func run*[T](io: IO[T]): T
 func strput*(str: string): IO[void]
@@ -18,7 +18,7 @@ func to_IO*[T](val: T): IO[T]
      
 # Definitions
 
-func flatmap*[T, U](io: IO[T], fn: T -> IO[U]): IO[U] = join(io.map(fn))
+func flatmap*[T, U](io: IO[T], fn: T -> IO[U]): IO[U] = join(map(io, fn))
 
 func lift*(fn: proc(): void): IO[void] =
   proc(): void = fn()
@@ -26,21 +26,10 @@ func lift*(fn: proc(): void): IO[void] =
 func lift*[T](fn: proc(): T): IO[T] =
   proc(): T = fn()
 
-func join*[T](io: IO[IO[T]]): IO[T] = io.map(run)
+func join*[T](io: IO[IO[T]]): IO[T] = map(io, run)
   
-func map*[T, U](io: IO[seq[T]], fn: T -> U): IO[seq[U]] =
-  proc(): seq[U] =
-    let list: seq[T] = io()
-
-    if list.len == 0:
-      @[]
-    else:
-      let
-        head: T          = list[0]
-        tail: seq[T]     = list[1..^1]
-        new:  IO[seq[T]] = to_IO tail
-
-      @[fn(head)] & run new.map(fn)
+func map*[T, U](io: IO[T], fn: T -> U): IO[U] =
+  proc(): U = fn(run(io))
 
 func readstr*(stream: FileDesc): IO[string] =
   case stream:

tests/test.nim

@@ -1,5 +1,5 @@
 import enso
-import std/[strformat, sugar]
+import std/[os, strformat, sugar]
 
 proc unsafe_void(str: string) =
   echo str
@@ -8,7 +8,12 @@ proc unsafe_int(str: string): int =
   echo str
   result = 1
 
-func add_two(x: int): int = x + 2
+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!")
@@ -20,15 +25,20 @@ func main() =
   out_void()
   run strput(fmt"{out_int()}")
 
+  let get_filename: IO[string] =
+    proc(): string =
+      let name: IO[string] = readstr(STDIN)
+      echo "Enter the file name:"
+      name()
+
   let
-    num_list:   IO[seq[int]] = to_IO @[1, 2, 3, 4, 5]
-    list_added: IO[seq[int]] = num_list.map(add_two)
+    nested: IO[IO[string]] = get_filename.map(check_file)
+    joined: IO[string]     = nested.join
 
-  run strput(fmt"{list_added()}")
+  run strput(joined())
 
-  run strput("Enter a string")
-  let read: IO[string] = readstr(STDIN)
-  run strput(read())
+  let flat: IO[string] = get_filename.flatmap(check_file)
+  run strput(flat())
 
 when isMainModule:
   main()