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Programming-Idioms

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  • Python

Idiom #206 Switch statement with strings

Execute different procedures foo, bar, baz and barfl if the string str contains the name of the respective procedure. Do it in a way natural to the language.

match str:
    case 'foo': foo()
    case 'bar': bar()
    case 'baz': baz()
    case 'barfl': barfl()

Python 3
switch = {'foo': foo, 
	'bar': bar, 
	'baz': baz, 
	'barfl': barfl
	}

switch_funct = switch.get(string)
if switch_funct : switch_funct()

Python does not natively support switch statements, but we can use a dictionary to replicate one.

The get() method will return the value of the given key if it exists and None otherwise where foo, bar, baz, and barf1 are all declared functions.

We then can check if the get method returned a value, and if it did, execute the returned function.
(def whitelist #{#'foo #'bar #'baz #'barfl})
(some-> str symbol resolve whitelist (.call))

str can contain fully qualified function name, like "clojure.string/upper-case".

set #{} is a function of an item: returns it back, if contains it, or nil otherwise.

#' is a literal for var.

some-> takes care of nil checks after each step.

This will throw, if whitelisted var contains not callable (e.g. number) or expects arguments.
New implementation...
< > ⌨
tkoenig 
match str:
    case 'foo': foo()
    case 'bar': bar()
    case 'baz': baz()
    case 'barfl': barfl()
switch = {'foo': foo, 
	'bar': bar, 
	'baz': baz, 
	'barfl': barfl
	}

switch_funct = switch.get(string)
if switch_funct : switch_funct()
(def whitelist #{#'foo #'bar #'baz #'barfl})
(some-> str symbol resolve whitelist (.call))
(some-> str {"foo" foo "bar" bar "baz" baz "barfl" barfl} (.call))

IDENTIFICATION DIVISION.
PROGRAM-ID. reverse string.
PROCEDURE DIVISION.
    EVALUATE str
       WHEN foo
	  PERFORM foo
       WHEN bar
          PERFORM bar
       WHEN baz
	  PERFORM baz 
       WHEN barfl
	  PERFORM barfl
       WHEN OTHER
	  CONTINUE
    END-EVALUATE.	
STOP RUN.
switch (str)
{
    case nameof(Foo):
        Foo();
        break;
    case nameof(Bar):
        Bar();
        break;
    case nameof(Baz):
        Baz();
        break;
    case nameof(Barfl):
        Barfl();
        break;
}
var myProc = {"foo": foo, 
              "bar": bar, 
              "baz": baz, 
              "barfl": barfl};

myProc[str]?.call();
  select case (str)
  case ("foo")
     call foo
  case ("bar")
     call bar
  case ("baz")
     call baz
  case ("barfl")
     call barfl
  end select
switch str {
case "foo":
	foo()
case "bar":
	bar()
case "baz":
	baz()
case "barfl":
	barfl()
}
case str of
  "foo" -> foo
  "bar" -> bar
  "baz" -> baz
  "barfl" -> barfl
switch (str) {
  case "foo":
    foo();
    break;
  case "bar":
    bar();
    break;
  case "baz":
    baz();
    break;
  case "barfl":
    barfl();
    break;
}
switch (str) {
    case "foo" -> foo();
    case "bar" -> bar();
    case "baz" -> baz();
    case "barfl" -> barfl();
}
switch (str){
	case "bar":
            bar();
            break;
        case "baz":
            baz();
            break;
        case "foo":
            foo();
            break;
        case "barfl":
            barfl();
            break;
        default:
            somethingElse();
    }
local procedures={
 foo=function() end,
 bar=function() end,
 baz=function() end,
 barfl=function() end,
}
local function process(str)
 local procedure=procedures[str]
 if procedure~=nil then
  procedure()
 end
end
process(str)
switch ($str) {
  case "foo":
    foo();
    break;
  case "bar":
    bar();
    break;
  case "baz":
    baz();
    break;
  case "barfl":
    barfl();
    break;
}

case str of
  'foo': foo;
  'bar': bar;
  'baz': baz;
  'barfl': barfl;
end;
my %proc = map { $_ => \&$_ } qw(foo bar baz barfl);
$proc{$str}->() if exists $proc{$str};
method(str).call if ["foo", "bar", "baz", "barfl"].include?(str)
match str {
    "foo" => foo(),
    "bar" => bar(),
    "baz" => baz(),
    "barfl" => barfl(),
    _ => {}
}

Select Case str
    Case NameOf(Foo)
        Foo()
    Case NameOf(Bar)
        Bar()
    Case NameOf(Baz)
        Baz()
    Case NameOf(Barfl)
        Barfl()
End Select
CallByName(receiver, str, CallType.Method)