Feature Request: Variable Number of Arguments

[DartBot]

This issue was originally filed by ador...@gmail.com

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It would be nice to have variable numbers of arguments, a la python splats.

This would make porting python code to dart much cleaner.

For example, I would like to do something like this:

void myFunc(arg1, arg2, *anyRemainingArgs){
  var extraArg1 = anyRemainingArgs[0];
  var extraArg2 = anyRemainingArgs[1];
  ...
}

[sgjesse]

Removed Type-Defect label.
Added Type-Enhancement, Area-Language, Triaged labels.

[DartBot]

This comment was originally written by @seaneagan

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Strawman:

varPositionals(required, [optional, String ...rest]) {
  assert(rest is List<String>);
}
varNamed (required, {optional, String ...rest}) {
  assert(rest is Map<Symbol, String>);
}

(...rest is used by ES6)

[DartBot]

This comment was originally written by adors...@gmail.com

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+1 for the Strawman in #­2. I like the '...' syntax, because it (1) semantically jibes for me, and (2) it echoes coffeescript varargs syntax, which folks are already familiar with.

[DartBot]

This comment was originally written by @zoechi

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As it's just another sytax for a parameter of type List, why not just stay with List?

[DartBot]

This comment was originally written by ado...@gmail.com

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I'm not sure that using a 'List' parameter has the effect I'm looking for.

If I used a 'List' parameter, wouldn't I have to explicitly put the arguments into a list when I call the function?

For example, if I have:

varPositionals (required, [optional, List theRest])

wouldn't I need to call this like:

varPositionals('required', 'optional', ['a', 'b', 'c'])

?

I'm looking instead for something more like python's behavior e.g. I want to call the function like this:

varPositionals('required', 'optional', 'a', 'b', 'c')

and have 'a', 'b', and 'c' get aggregated into the variable 'theRest'.

I hope that this helps to clarify.

[DartBot]

This comment was originally written by @zoechi

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I understand your request but I'm not sure if special syntax is worth this little (IMHO) gain.

[DartBot]

This comment was originally written by yu.asa...@gmail.com

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This would make porting python code to dart much cleaner.

As a user of Dart, I personally do not find it important to make it easy to port code from Python to Dart, or from any language for that matter (perhaps except for JavaScript). After all, Dart and Python are different languages.

I am not saying that supporting variadic functions in Dart is useless. But “Python supports them, so Dart should also support them to make porting easy” is a weak argument.

By the way, it is possible to emulate variadic functions in Dart by a dirty hack in case you need them for some reason. See my post at http://yuasakusa.github.io/dart/2014/01/23/dart-variadic.html.

[DartBot]

This comment was originally written by ado...@gmail.com

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Yah, I agree that supporting varargs just for the sake of porting python code is not a good argument.

However, I would say that supporting varargs for the sake of having a clean, flexible, readable langauge is a good argument.

We can get around the lack of vararg support using tricks like the one described in Yu Asakusa's blog post. (Nice, by the way!). But to me built-in vararg support would still be nice to have.

At this point I suppose the decision on this rests in the hands of the Dart committee (or however these things get decided? Is there a benevolent dart-tator for life?)

[gbracha]

Set owner to @gbracha.
Added Accepted label.

[gil0mendes]

I see that task has been assigned to someone... but it's been a year since the last activity... my question is... how much longer we have to wait for this syntax?

[seaneagan]

Someone will need to create a dart enhancement proposal for it first.

[jacob314]

Supporting variable numbers of arguments would improve console logging methods in dart:html and for Flutter.

[segfaultmedaddy]

Is it possible that this feature will be included into the Dart 2.0?