Please implement comparison (e.g. <=,<,>,>=) operators for String

[DartBot]

This issue was originally filed by jack.palevich@gmail.com

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operator<, operator<=, etc.

They can be implemented in terms of the existing Comparable.compareTo()

(It would be neat if Dart knew to automatically implement the relational operators for any class that implemented Comparable.)

[DartBot]

This comment was originally written by drfibonacci@google.com

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

[floitschG]

Removed Area-Language label.
Added Area-Library label.

[DartBot]

This comment was originally written by @seaneagan

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The suggestion to:

"automatically implement the relational operators for any class that implemented Comparable"

... could be done via issue #33 (mixins). Mixins would have an implicit interface just like classes, so Comparable could be an abstract mixin:

mixin Comparable<T extends Comparable> {
  int compareTo(T other);
  bool operator < (T other) => compareTo(other) < 0;
  bool operator <= (T other) => this < other || this == other;
  bool operator > (T other) => !(this <= other);
  bool operator >= (T other) => !(this < other);
}

interfaces could extend Comparable, and classes could both implement and mixin Comparable, and then merely define compareTo. I would get rid of compareTo though since it makes it ambiguous as to whether <= and >= should use == or compareTo(other) == 0. Instead < could be the abstract method which needs to be implemented, like so:

mixin Comparable<T extends Comparable> {
  bool operator < (T other);
  bool operator <= (T other) => this < other || this == other;
  bool operator > (T other) => !(this <= other);
  bool operator >= (T other) => !(this < other);
}

Then you could do something like:

interface String extends Comparable factory StringFactory {/.../}
class StringFactory extends Comparable implements String {
  //...
  operator < (String other) native;
}

[floitschG]

There are currently no plans to add comparison operators to Strings.
We have (reluctantly) added a compareTo method on Strings to allow sorting, but there isn't really a good natural order on Strings. We don't want to give this impression by adding comparison operators.

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Added NotPlanned label.