0000577: composite enums

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Date Submitted

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0000577

mercury

Feature Request

public

2025-08-13 03:27

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Assigned To

Priority

normal

Severity

minor

Reproducibility

have not tried

Status

new

Resolution

open

Product Version

Target Version

Fixed in Version

Summary

0000577: composite enums

Description

Types such as the ext type in the compiler, which have

- several function symbols,
- all of which one argument,
- and all those arguments have types that are effectively enums,

should be themselves represented as one large enum.

Given e.g.

:- type t
---> f(t1)
; g(t2).

where t1 is an enum with values 0-12 and t2 is an enum
with values 0-42, then t should be such a "composite enum"
with values 0-55, with values 0-12 corresponding to function
symbol f, and values 13-55 corresponding to g (with the value
of g's argument being t's value minus 13.

The natural way to do switches on such composite enums
would be by binary search, not on the raw values, but on
the dividing lines between the integer ranges assigned to
the function symbols. Each binary step would rule out half
(rounded down) of the remaining possible function symbols.

Date Modified	Username	Field	Change
Issue History
2025-08-13 03:27	zs	New Issue

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