Generic boolean operators #1008
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Boolean operators, such as `==`, `!=`, `<`, etc, are currently defined
by `std::cmp::{Eq,Ord}`, and require that they return `bool`. It would
be a useful generalization to allow them to return alternative types, in
similar form to `std::ops`.
| MyModel.my_field == 42 & MyModel.my_other_field > 17 | ||
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| It is my opinion that operators are _significantly_ more readable and parsable than operators in this context, and that the return value not being a boolean is apparent in the context. That being said, if allowing the boolean operators to return non-boolean values was not acceptable, then this would probably be the next best option for my use-case. |
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[…] operators are significantly more readable and parsable than methods […]
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In principle, I find that a good idea. It's also somewhat problematic that the standard library mixes operator definition with the concept of equivalence from a mathematical point of view. However, it is almost certainly too late for this change. |
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I would be for keeping The only time you wouldn't want this is if you were trying to form some sort of calculation to perform later, or to create some sort of custom closure. For something you would execute later in the same program, like a filter, it would be better just to make a closure. For SQL/database stuff, just use a macro that turns >/</== into calling methods on your own trait. I wouldn't want to pay the cost of not knowing what ==/>/< will do, just to allow for some lazy evaluation or SQL using >/</==. It is much more valuable to have each operator do what you expect, evaluating now, than allow for forming other structures. |
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This proposal is a subset of a previously proposed (and postponed) alternative. Therefore, I'm marking this as postponed under #420. Thanks for the suggestion! |
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Boolean operators, such as
==,!=,<, etc, are currently defined bystd::cmp::{Eq,Ord}, and require that they returnbool. It would be a useful generalization to allow them to return alternative types, in similar form tostd::ops.Previous discussions on the Rust Reddit, Rust Internals Discourse, and IRC.
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