Implement a well defined ordering among types #1702
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This builds on the previous changes to implement a total ordering by replacing the dependency on the address at which various types are defined (which is effectively random) with an explicit ordering. For types without an explicit ordering it uses an ordering based on the order in which each unknown type is compared. This makes the ordering predictable based on the execution of Elvish code without regard to unpredictable factors such as the layout of data structures in the Elvish binary. Note that the use of mechanisms like the `peach` command can introduce unpredictable ordering of unknown value types since this change handles unknown types at run time and thus, in theory, produce different results when Elvish code that invokes `compare &total` or `order &total` is run concurrently. Whereas the prior logic is not affected by the parallelism of Elvish code. Nonetheless, I maintain that the predictability of ordering heterogenous values introduced by this change is a net positive since the new behavior will be predictable and reproducible (as a practical matter) while the prior logic (based on the random layout of data structures in the Elvish binary) is neither. Related elves#1495
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This builds on the previous changes to implement a total ordering by replacing the dependency on the address at which various types are defined (which is effectively random) with an explicit ordering. For types without an explicit ordering it uses an ordering based on the order in which each unknown type is compared. This makes the ordering predictable based on the execution of Elvish code without regard to unpredictable factors such as the layout of data structures in the Elvish binary.
Note that the use of mechanisms like the
peachcommand can introduce unpredictable ordering of unknown value types since this change handles unknown types at run time and thus, in theory, produce different results when Elvish code that invokescompare &totalororder &totalis run concurrently. Whereas the prior logic is not affected by the parallelism of Elvish code. Nonetheless, I maintain that the predictability of ordering heterogenous values introduced by this change is a net positive since the new behavior will be predictable and reproducible (as a practical matter) while the prior logic (based on the random layout of data structures in the Elvish binary) is neither.Related #1495