The following code snippet is from reasonml, a dialect from ocaml,
type schoolPerson = Teacher | Director | Student(string);
let greeting = person =>
switch (person) {
| Teacher => "Hey Professor!"
| Director => "Hello Director."
| Student("Richard") => "Still here Ricky?"
| Student(anyOtherName) => "Hey, " ++ anyOtherName ++ "."
};
I know Nim has object variant and generic feature, but How can I express type with "payload" as
("Richard")One way might be:
type
spKind = enum
spkTeacher,spkDirector,spkStudent
SchoolPerson = object
case kind:spKind
of spkStudent:
name: string
else: discard
proc greeting(sp: SchoolPerson):string =
case sp.kind
of spkTeacher: "Hey Prof!"
of spkDirector: "Sup Guv"
of spkStudent:
case sp.name
of "Richard": "Still here Dick?"
else: "Hi " & sp.name & "."
echo greeting(SchoolPerson(kind:spkStudent,name:"George"
I guess this is more concise:
proc greeting(sp: SchoolPerson):string =
let (kind, name) = (sp.kind, sp.name)
case (kind, name):
of (spkTeacher, _): "Hey Prof!"
of (spkDirector, _): "Sup Guv"
of (spkStudent, "Richard"): "Still here Dick?"
else: "Hi " & sp.name & "."
fusion/matching actually has a special treatment of kind, so you can write:
case sp
of Teacher(): "Hey Prof!"
of Director(): "Sup Guv"
of Student(name: "Richard"): "Still here Dick?"
of Student(name: @name): "Hi " & name & "."