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compiler/mlds.m:
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Fergus Henderson
2003-12-05 04:19:30 +00:00
parent b3eaef4f2b
commit 3a086506c0
1 changed files with 28 additions and 3 deletions
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compiler/mlds.m
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@@ -47,6 +47,8 @@
% Mercury module names map directly to MLDS package names, except that % Mercury module names map directly to MLDS package names, except that
% modules in the Mercury standard library map get a `mercury' prefix, % modules in the Mercury standard library map get a `mercury' prefix,
% e.g. `mercury.builtin', `mercury.io', `mercury.std_util', etc. % e.g. `mercury.builtin', `mercury.io', `mercury.std_util', etc.
% [Rationale: omitting the `mercury' prefix would lead to namespace
% pollution in the generated target language code.]
% 2. Procedure names % 2. Procedure names
% %
@@ -80,9 +82,21 @@
% With the `--copy-out' option, arguments with top_out modes will be returned % With the `--copy-out' option, arguments with top_out modes will be returned
% by value. This requires the target language to support multiple return % by value. This requires the target language to support multiple return
% values. The MLDS->target code generator can of course handle that by mapping % values. The MLDS->target code generator can of course handle that by mapping
% functions with multiple return values into functions that return a struct. % functions with multiple return values into functions that return a struct,
% array, or tuple.
% With the `--nondet-copy-out' option, arguments for nondet procedures with % With the `--nondet-copy-out' option, arguments for nondet procedures with
% top_out modes will be passed as arguments to the continuation. % top_out modes will be passed as arguments to the continuation.
%
% [Rationale: this mapping is designed to be as simple as possible,
% and to map as naturally to the target language as possible.
% The complication with the `--copy-out' and `--nondet-copy-out'
% options is needed to cater to different target languages.
% Some target languages (e.g. C) fully support pass-by-reference,
% and then it is most consistent to use it everywhere.
% Some (e.g. IL) support pass-by-reference, but don't allow references
% to be stored in the environment structs needed for continuations,
% and so can't use pass-by-reference for nondet procedures.
% Others (e.g. Java) don't support pass-by-reference at all.]
% 4. Variables % 4. Variables
% %
@@ -129,8 +143,19 @@
% 7. Data constructors. % 7. Data constructors.
% %
% [XXX Not yet documented or implemented] % With --high-level-data, Mercury data constructors normally get mapped to
% [XXX Also need to think about equivalence types and no_tag types] % MLDS types nested within the MLDS type for the Mercury data type to which
% the constructors belong. There are some exceptions; see ml_type_gen.m
% for full details. The MLDS type name includes the constructor arity.
% [Rationale: Mercury allows data constructors to be overloaded on
% their result type within a single module, and also allows them
% to be overloaded on arity within a single type. Nesting resolves
% the first problem, and keeping the arity in the MLDS type name
% resolves the second.]
% XXX There is a problem in the Java back-end with Mercury types for which
% the constructor name is the same as the type name.
%
% XXX Also need to think about equivalence types and no_tag types.
% 8. Insts and modes % 8. Insts and modes
% %