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Estimated hours taken: 4 Translated plain text docs to HTML. This obviously creates a dual update problem. We should solve this by putting the plain text docs in the attic and retaining the HTML. Also added the HTML files to the Mmakefile so they are installed on the web pages. The other documents in compiler/notes will be HTMLized soon. compiler/notes/ Mmakefiles ALLOCATION.html AUTHORS.html CODING_STANDARDS.html COMPILER_DESIGN.html GC_AND_C_CODE.html GLOSSARY.html MODULE_SYSTEM.html RELEASE_CHECKLIST.html REVIEWS.html TODO.html
344 lines
8.4 KiB
HTML
344 lines
8.4 KiB
HTML
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<html>
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<head>
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<title>
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Mercury Coding Standard for the Mercury Project
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</title>
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</head>
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<body
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bgcolor="#ffffff"
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text="#000000"
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>
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<hr>
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<!-------------------------->
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<h1>
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Mercury Coding Standard for the Mercury Project</h1>
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<hr>
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<!-------------------------->
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<h2> Use of language features </h2>
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<p>
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Language features that do not work in SICStus Prolog
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(including functions, reverse modes of arithmentic,
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the NU-Prolog syntax for negation and if-then-else,
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and code requiring mode reordering) should not be used
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in the Mercury compiler --- at least not until we
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have implemented a proper debugger.
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<p>
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<h2> Documentation </h2>
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<p>
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Each module should contain header comments which state
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the module's name, main author(s), and purpose, and
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give an overview of what the module does, what are the
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major algorithms and data structures it uses, etc.
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<p>
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Each type or predicate that is exported from a module should have
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sufficient documentation that it can be understood without reference
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to the module's implementation section.
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<p>
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Each predicate other than trivial access predicates should have
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a short comment describing what the predicate is supposed to do,
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and what the meaning of the arguments is.
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<p>
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There should be a comment for each field of a structure saying
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what the field represents.
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<p>
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Any user-visible changes such as new compiler options or new
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features should be documented in appropriate section
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of the Mercury documentation (usually the Mercury User's Guide
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and/or the Mercury Reference Manual). Any major new features
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should be documented in the NEWS file, as should even small
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changes to the library interface, or anything else that might
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cause anyone's existing code to break.
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<p>
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Any new compiler modules or other major design changes should
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be documented in `compiler/notes/COMPILER_DESIGN'.
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<p>
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<h2> Naming </h2>
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<p>
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Variables should always be given meaningful names,
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unless they are irrelevant to the code in question.
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For example, it is OK to use single-character names
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in an access predicate which just sets a single
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field of a structure, such as
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<pre>
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bar_set_foo(Foo, bar(A, B, C, _, E), bar(A, B, C, Foo, E)).
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</pre>
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Variables which represent different states or different versions
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of the same entity should be named Foo0, Foo1, Foo2, ..., Foo.
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<p>
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Predicates which get or set a field of a structure or ADT should
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be named bar_get_foo and bar_set_foo respectively, where bar
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is the name of the structure or ADT and foo is the name of the field.
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<p>
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<h2> Coding </h2>
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<p>
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Your code should make as much reuse of existing code as possible.
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"cut-and-paste" style reuse is highly discouraged.
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<p>
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Your code should be efficient. Performance is a quite
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serious issue for the Mercury compiler.
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<p>
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No fixed limits please!
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(If you really must have a fixed limit, include detailed documentation
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explaining why it was so hard to avoid.)
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<p>
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<h2> Error Handling </h2>
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<p>
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Code should check for both erroneous inputs from the user and also
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invalid data being passed from other parts of the Mercury compiler.
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You should also always check to make sure that the routines that you
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call have succeed; make sure you don't silently ignore failures. (This
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last point almost goes without saying in Mercury, but is particularly
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important to bear in mind if you are writing any C code or shell
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scripts, or if you are interfacing with the OS.)
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<p>
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Calls to error/1 should always indicate an internal software error, not
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merely incorrect inputs from the user, or failure of some library routine
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or system call.
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<p>
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Error messages should follow a consistent format. For compiler error
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messages, each line should start with the source file name and line
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line number in "%s:%03d: " format (but use prog_out__write_context --
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we may want to change this format later, e.g. to include column
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numbers). Compiler error messages should be complete sentences; they
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should start with a capital letter and end in a full stop. For error
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messages that are spread over more than one line (as are most of them),
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the second and subsequent lines should be indented two spaces. If the
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`--verbose-errors' option was set, you should print out additional text
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explaining in detail what the error message means and what the likely
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causes are.
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<p>
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Error messages from the runtime system should begin with the text
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"Mercury Runtime:", preferably by using the fatal_error() routine.
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<p>
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If a system call or C library function that sets errno fails, the
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error message should be printed with perror() or should contain
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strerror(errno). If it was a function manipulating some file, the
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error message should include the filename.
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<p>
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<h2> Layout </h2>
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Code should be indented consistently.
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Tabs should be every 8 spaces.
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Indentation should be one tab per level of indentation.
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except for highly intended code which may be
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indented at 4 spaces per level of indentation.
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Each line should not extend beyond 79 characters,
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unless this is necessary due to the use of long string literals.
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If-then-elses should always be parenthesized,
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except that an if-then-else that occurs as the else
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part of another if-then-else doesn't need to be parenthesized.
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The semicolon of a disjunction should never be at the
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end of a line -- put it at the start of the next line instead.
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The condition of an if-then-else can either be on the same
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line as the opening parenthesis and the `->',
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<pre>
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( test1 ->
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goal1
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; test2 ->
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goal2
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;
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goal
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)
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</pre>
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or, if the test is complicated, it can be on a line of its own:
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<pre>
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(
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very_long_test_that_does_not_fit_on_one_line(VeryLongArgument1,
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VeryLongArgument2)
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->
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goal1
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;
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test2a,
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test2b,
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->
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goal2
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;
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test3 % would fit one one line, but separate for consistency
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->
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goal3
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;
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goal
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).
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</pre>
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Type definitions should be formatted in the following style:
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<pre>
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:- type my_type
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---> my_type(
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some_other_type % comment explaining it
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).
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:- type some_other_type == int.
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:- type foo
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---> bar(
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int, % comment explaining it
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float % comment explaining it
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)
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; baz
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; quux.
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</pre>
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If an individual clause is long, it should be broken into sections,
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and each section should have a "block comment" describing what it does;
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blank lines should be used to show the separation into sections.
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Comments should precede the code to which they apply, rather than
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following it.
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<pre>
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%
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% This is a block comment; it applies to the code in the next
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% section (up to the next blank line).
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%
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blah,
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blah,
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blahblah,
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blah,
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</pre>
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If a particular line or two needs explanation, a "line" comment
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<pre>
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% This is a "line" comment; it applies to the next line or two
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% of code
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blahblah
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</pre>
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or an "inline" comment
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<pre>
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blahblah % This is an "inline" comment
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</pre>
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should be used.
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At a higher level, code should be grouped into bunches of related
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predicates, functions, etc., and sections of code that are conceptually
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separate should be separated with dashed lines:
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<pre>
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%---------------------------------------------------------------------------%
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Double-dashed lines, i.e.
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%---------------------------------------------------------------------------%
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%---------------------------------------------------------------------------%
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</pre>
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can also be used to indicate divisions into major sections.
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<h2> Testing </h2>
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<p>
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Every change should be tested before being committed.
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The level of testing required depends on the nature of the change.
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If this change fixes an existing bug, and is not likely to introduce
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any new bugs, then just compiling it and running some tests
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by hand is sufficient. If the change might break the compiler,
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you should run a bootstrap check (using the `bootcheck' script)
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before committing. If the change means that old versions of
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the compiler will not be able to compile the new version of the
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compiler, you must notify all the other Mercury developers.
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<p>
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In addition to testing before a change is committed, you need to make
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sure that the code will not get broken in the future by adding tests to
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the test suite. Every time you add a new feature, you should add some
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test cases for that new feature to the test suite. Every time you fix
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a bug, you should add a regression test to the test suite.
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<p>
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<h2> Committing changes </h2>
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<p>
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Before committing a change, you should get someone else to review your
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changes.
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<p>
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The file "REVIEWS" contains more information on review policy.
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<hr>
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<!-------------------------->
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Last update was $Date: 1997-04-03 05:17:34 $ by $Author: aet $@cs.mu.oz.au. <br>
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</body>
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</html>
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