proc p(x: int, xIsSet: bool) = ...
or smth like
type IntOrNil = object
x: int
isSet: bool
proc p(x: IntOrNil) = (if x.isSet: echo x.x else: #[ something else ]#
discard)
# additional procs may be added for such a type
proc `$`(x: IntOrNil): string = (if x.isSet: $x else: "nil")
converter x(x: IntOrNil): int =
if x.isSet:
return x.x
else:
raise newException(ValueError,"int to nil conversion")
# usage
p(IntOrNil(x: 5, isSet: false))
var v = IntOrNil(x: 5, isSet: true)
echo v+2
v.isSet = false
try:
echo v+2
except ValueError:
echo "v not set!"
# or so:
echo (try: $(v+2) except: "v not set!")
Like in most other languages.
Yet you can search github for "nim maybe" and the like queries, there were some
libs.
