mirror of
https://github.com/Mercury-Language/mercury.git
synced 2026-04-22 21:03:53 +00:00
f1fc2f6cb3
compiler/accumulator.m:
Give some predicates more meaningful names.
Fix the copyright attribution.
compiler/assertion.m:
Put related predicates next to each other.
Give some predicates more meaningful names.
Keep private the predicates that do not need to be exported.
compiler/hlds_promise.m:
Merge the three separate interface sections into one; this module
is not big enough to benefit from having them separate.
Stop using pred_ids as keys in exclusive_tables.
compiler/check_promise.m:
Conform to the change in hlds_promise.m.
Add some comments.
compiler/notes/promise_ex.html:
Fix some bit rot, and note some other bit rot.
140 lines
3.6 KiB
HTML
140 lines
3.6 KiB
HTML
<!--
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vim: ts=4 sw=4 expandtab ft=html
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-->
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<html>
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<head>
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<title>Promise Ex Declarations</title>
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</head>
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<body>
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<h1>Promise Ex Declarations</h1>
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This document is a description of promise ex declarations,
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which are currently unfinished and as such are undocumented
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in the reference manual.
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<p>
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<h2>Syntax</h2>
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There are currently three promise ex declarations:
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promise_exclusive, promise_exhaustive, and promise_exclusive_exhaustive.
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They are used to denote determinism properties of a disjunction,
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and denote either exclusivity, exhaustiveness, or both.
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The examples of each, given below,
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also show the different ways that existential quantification can be handled.
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<ul>
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<li>
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Mutual exclusivity:
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<pre>
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:- all [X, Y] promise_exclusive
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some [Z] (
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p(X, Y, Z)
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;
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q(X, Y, Z)
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).
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</pre>
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<li>
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Exhaustiveness:
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<pre>
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:- all [X] promise_exhaustive
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(
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p(X, _)
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;
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q(X, _)
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).
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</pre>
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<li>
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Both together:
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<pre>
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:- all [X] promise_exclusive_exhaustive
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some [Y] (
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p(X, Y)
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;
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q(X, Y, Z)
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).
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</pre>
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</ul>
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All three declarations are restricted in the following ways:
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<ul>
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<li>
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Any variable that occurs in more than one disjunct
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must be explicitly quantified.
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<li>
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Any variable occurring in only one disjunct is existentially quantified.
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This is similarly applicable when an underscore is used in place of a variable.
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</ul>
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<p>
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<h2>Development</h2>
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This tracks the use of promise ex declarations through the compiler,
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and may be useful as a quick summary of the current state of development.
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Items marked with an asterisk (*) are not yet implemented.
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Places where data structures etc. have been defined are in italics.
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(The module names listed have suffered bit rot.)
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<ol>
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<li>
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The declarations enter the parse tree.
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<ul>
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<li>
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<i>The operators are defined</i> (library/ops.m).
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<li>
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<i>The structure for promise ex declarations in the parse tree
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is defined</i> (prog_data.m).
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<li>
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They are parsed and entered into the parse tree (parse_item.m).
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</ul>
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<li>
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They may be pretty printed (mercury_to_mercury.m, parse_tree_out.m).
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<li>
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They are error checked, and entered into the HLDS as dummy predicates.
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<ul>
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<li>
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Error checking (make_hlds.m).
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<li>
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Entering of declarations into the HLDS as dummy predicates (make_hlds.m).
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</ul>
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<li>
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They go through typechecking as predicates.
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After the typecheck, post-typecheck and purity passes of the front-end,
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they are removed from processing as predicates
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and entered into the appropriate table in the HLDS (by check_promises.m).
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<ul>
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<li>
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Post typechecking processing initiated for promise ex declarations
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(purity.m).
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<li>
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promise_exclusive and promise_exhaustive declarations
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are indexed by the predicate calls made in them
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in the exclusive table (post_typecheck.m).
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<li>
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<i>Definition of exclusive table as part of HLDS,
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and operations on the table</i> (hlds_module.m).
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<li>
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(*) Where a promise_exhaustive declaration
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is paired with a promise_exclusive declaration,
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they are merged into a promise_exclusive_exhaustive declaration;
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otherwise the promise_exhaustive declaration
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is entered in the exhaustive table of the HLDS (post_typecheck.m).
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<li>
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(*) <i>Definition of exhaustive table as part of HLDS, and
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operations on the table</i> (hlds_module.m).
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</ul>
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<li>
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(*) Exclusivity information is used during switch detection,
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and where it leads to a full switch being made,
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applicable exhaustiveness information is also used (switch_detection.m).
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<li>
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(*) Exhaustiveness information is used
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during determinism analysis (det_analysis.m)
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or as an add-on to switch detection (switch_detection.m).
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</ol>
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</body>
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</html>
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