Merge branch 'devel' of github.com:nim-lang/Nim into devel

lib/pure/options.nim

@@ -15,7 +15,7 @@
 ## A value of type ``Option[T]`` either contains a value `x` (represented as
 ## ``some(x)``) or is empty (``none(T)``).
 ##
-## This can be useful when you have a value that can be present or not.  The
+## This can be useful when you have a value that can be present or not. The
 ## absence of a value is often represented by ``nil``, but it is not always
 ## available, nor is it always a good solution.
 ##
@@ -67,10 +67,8 @@
 ##     assert(false)  # This will not be reached
 ##   except UnpackError:  # Because an exception is raised
 ##     discard
-
 import typetraits
 
-
 type
   Option*[T] = object
     ## An optional type that stores its value and state separately in a boolean.
@@ -78,7 +76,6 @@ type
     has: bool
   UnpackError* = ref object of ValueError
 
-
 proc some*[T](val: T): Option[T] =
   ## Returns a ``Option`` that has this value.
   result.has = true
@@ -88,14 +85,12 @@ proc none*(T: typedesc): Option[T] =
   ## Returns a ``Option`` for this type that has no value.
   result.has = false
 
-
 proc isSome*[T](self: Option[T]): bool =
   self.has
 
 proc isNone*[T](self: Option[T]): bool =
   not self.has
 
-
 proc unsafeGet*[T](self: Option[T]): T =
   ## Returns the value of a ``some``. Behavior is undefined for ``none``.
   assert self.isSome
@@ -110,12 +105,11 @@ proc get*[T](self: Option[T]): T =
 
 proc get*[T](self: Option[T], otherwise: T): T =
   ## Returns the contents of this option or `otherwise` if the option is none.
-  if self.isSome:
+  if self.has:
     self.val
   else:
     otherwise
 
-
 proc map*[T](self: Option[T], callback: proc (input: T)) =
   ## Applies a callback to the value in this Option
   if self.has:
@@ -123,12 +117,27 @@ proc map*[T](self: Option[T], callback: proc (input: T)) =
 
 proc map*[T, R](self: Option[T], callback: proc (input: T): R): Option[R] =
   ## Applies a callback to the value in this Option and returns an option
-  ## containing the new value. If this option is None, None will be returned
+  ## containing the new value. If this option is None, None will be returned.
   if self.has:
-    some[R]( callback(self.val) )
+    some[R](callback(self.val))
   else:
     none(R)
 
+proc flatten*[A](self: Option[Option[A]]): Option[A] =
+  ## Remove one level of structure in a nested Option.
+  if self.has:
+    self.val
+  else:
+    none(A)
+
+proc flatMap*[A, B](self: Option[A], callback: proc (input: A): Option[B]): Option[B] =
+  ## Applies a callback to the value in this Option and returns an
+  ## option containing the new value. If this option is None, None will be
+  ## returned. Similar to ``map``, with the difference that the callback
+  ## returns an Option, not a raw value. This allows multiple procs with a
+  ## signature of ``A -> Option[B]`` (including A = B) to be chained together.
+  map(self, callback).flatten()
+
 proc filter*[T](self: Option[T], callback: proc (input: T): bool): Option[T] =
   ## Applies a callback to the value in this Option. If the callback returns
   ## `true`, the option is returned as a Some. If it returns false, it is
@@ -138,21 +147,18 @@ proc filter*[T](self: Option[T], callback: proc (input: T): bool): Option[T] =
   else:
     self
 
-
 proc `==`*(a, b: Option): bool =
   ## Returns ``true`` if both ``Option``s are ``none``,
   ## or if they have equal values
   (a.has and b.has and a.val == b.val) or (not a.has and not b.has)
 
-
-proc `$`*[T]( self: Option[T] ): string =
+proc `$`*[T](self: Option[T]): string =
   ## Returns the contents of this option or `otherwise` if the option is none.
   if self.has:
     "Some(" & $self.val & ")"
   else:
     "None[" & T.name & "]"
 
-
 when isMainModule:
   import unittest, sequtils
 
@@ -198,12 +204,12 @@ when isMainModule:
         check false
 
     test "get with a default value":
-      check( some("Correct").get("Wrong") == "Correct" )
-      check( stringNone.get("Correct") == "Correct" )
+      check(some("Correct").get("Wrong") == "Correct")
+      check(stringNone.get("Correct") == "Correct")
 
     test "$":
-      check( $(some("Correct")) == "Some(Correct)" )
-      check( $(stringNone) == "None[string]" )
+      check($(some("Correct")) == "Some(Correct)")
+      check($(stringNone) == "None[string]")
 
     test "map with a void result":
       var procRan = 0
@@ -212,11 +218,38 @@ when isMainModule:
       intNone.map(proc (v: int) = check false)
 
     test "map":
-      check( some(123).map(proc (v: int): int = v * 2) == some(246) )
-      check( intNone.map(proc (v: int): int = v * 2).isNone )
+      check(some(123).map(proc (v: int): int = v * 2) == some(246))
+      check(intNone.map(proc (v: int): int = v * 2).isNone)
 
     test "filter":
-      check( some(123).filter(proc (v: int): bool = v == 123) == some(123) )
-      check( some(456).filter(proc (v: int): bool = v == 123).isNone )
-      check( intNone.filter(proc (v: int): bool = check false).isNone )
+      check(some(123).filter(proc (v: int): bool = v == 123) == some(123))
+      check(some(456).filter(proc (v: int): bool = v == 123).isNone)
+      check(intNone.filter(proc (v: int): bool = check false).isNone)
 
+    test "flatMap":
+      proc addOneIfNotZero(v: int): Option[int] =
+        if v != 0:
+          result = some(v + 1)
+        else:
+          result = none(int)
+
+      check(some(1).flatMap(addOneIfNotZero) == some(2))
+      check(some(0).flatMap(addOneIfNotZero) == none(int))
+      check(some(1).flatMap(addOneIfNotZero).flatMap(addOneIfNotZero) == some(3))
+
+      proc maybeToString(v: int): Option[string] =
+        if v != 0:
+          result = some($v)
+        else:
+          result = none(string)
+
+      check(some(1).flatMap(maybeToString) == some("1"))
+
+      proc maybeExclaim(v: string): Option[string] =
+        if v != "":
+          result = some v & "!"
+        else:
+          result = none(string)
+
+      check(some(1).flatMap(maybeToString).flatMap(maybeExclaim) == some("1!"))
+      check(some(0).flatMap(maybeToString).flatMap(maybeExclaim) == none(string))

lib/system.nim

@@ -1443,6 +1443,10 @@ elif defined(genode):
     importcpp: "genodeEnv->parent().exit(@); Genode::sleep_forever()",
     header: "<base/sleep.h>".}
 
+elif defined(nodejs):
+  proc quit*(errorcode: int = QuitSuccess) {.magic: "Exit", 
+    importc: "process.exit", noreturn.}
+
 else:
   proc quit*(errorcode: int = QuitSuccess) {.
     magic: "Exit", importc: "exit", header: "<stdlib.h>", noreturn.}