diff --git a/lib/pure/options.nim b/lib/pure/options.nim
index 2abb80016..ad63bbcb6 100644
--- a/lib/pure/options.nim
+++ b/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))
diff --git a/lib/system.nim b/lib/system.nim
index e642eb335..dc3152faf 100644
--- a/lib/system.nim
+++ b/lib/system.nim
@@ -1443,6 +1443,10 @@ elif defined(genode):
importcpp: "genodeEnv->parent().exit(@); Genode::sleep_forever()",
header: "".}
+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: "", noreturn.}