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Use of ?: in static const #5558

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DartBot opened this issue Sep 28, 2012 · 6 comments
Closed

Use of ?: in static const #5558

DartBot opened this issue Sep 28, 2012 · 6 comments
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@gbracha
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area-language Dart language related items (some items might be better tracked at github.com/dart-lang/language). type-enhancement A request for a change that isn't a bug

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@DartBot
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DartBot commented Sep 28, 2012

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

Would it be possible to allow use of ?: operator in static consts?
This allows them to be used a little like cpp's #ifdef.

const bool GRAVITY_ENABLED = true;
const num GRAVITY_Y = GRAVITY_ENABLED ? -9.81 : 0;

Per forum discussion https://groups.google.com/a/dartlang.org/d/topic/misc/RaFkab2-oU8/discussion

(FAO Gilad.)
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DartBot commented Sep 28, 2012

This comment was originally written by ladicek@gmail.com

I think that the ?: ternary operator could easily be made compile-time constant, provided that its operands are also constants (and the condition is bool). This would increate expressivity of compile-time constants a lot.

In other words, I want this added to section 11.1 of the spec:

  A constant expression is one of the following:

  - ...
  - ...
  - An expression of the form e1 ? e2 : e3 where e1 is a constant expression that evaluates to a boolean value and e2 and e3 are constant expressions.

@kasperl
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kasperl commented Oct 5, 2012

cc @floitschG.
Added Area-Language, Triaged labels.

@gbracha
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gbracha commented Nov 7, 2012

It's perfectly doable. Of course, the effect is just a rather minor convenience.

Set owner to @gbracha.
Removed Type-Defect label.
Added Type-Enhancement, Accepted labels.

@floitschG
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Issue #12981 has been merged into this issue.

@rakudrama
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I have on several occasions needed something like this.
The latest example was trying to pick between a VM and dart2js implementation of a class.

@gbracha
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gbracha commented Aug 25, 2014

Added Done label.

@DartBot DartBot added Type-Enhancement area-language Dart language related items (some items might be better tracked at github.com/dart-lang/language). labels Aug 25, 2014
@kevmoo kevmoo added type-enhancement A request for a change that isn't a bug and removed type-enhancement labels Mar 1, 2016
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