NEWS for Mercury 22.01.9
========================

This is a bug-fix release.

* [Github issue #147]. We have fixed a const correctness issue in the C
  runtime that was causing warnings to be emitted with recent versions of
  GCC and the GNU C library.

* [Mantis bug #566]. We have fixed an issue that was causing GNU Make 4.4.0
  and above to emit warnings about undefined variables.

* We have improved the compatibility of the `configure` script with older
  versions of `bash`.

* We have fixed a bug in the C# implementation of
  `random.system_rng.generate_uint8/4` that caused it to throw an exception
  after successfully generating a random value.

* We have added the missing lower-bound checks on the time components of the
  predicate `calendar.init_date/8`.

* We have fixed two bugs in `calendar.duration_from_string/2` that caused it
  to accept invalid duration strings. The first was that the string "P" was
  incorrectly being accepted as the zero duration; the second was that duration
  strings containing a fractional second component with no whole number part
  (e.g. "PT.5S") were incorrectly being accepted.

* We have fixed a bug in `calendar.duration/2` that caused it to compute
  an incorrect duration, or abort, for some pairs of dates whose difference
  required borrowing days across months of differing length.

* `calendar.date_from_string/2` and `calendar.duration_from_string/2` now
   check for integer overflow in their components.

* We have fixed bugs in the C# and Java implementations of
  `math.unchecked_log2/1` that caused target language compilation errors
  when compiling with `--intermodule-optimisation`.

* We have fixed a bug where using C# contextual keywords as the names
  of Mercury entities (e.g. module names) could cause invalid C# to be
  generated.

* We have fixed a bug where a Mercury type containing a data constructor whose
  name begins with a digit could cause invalid C# code to be generated.

* All remaining Java security manager dependencies have been replaced,
  since the security manager is deprecated.

* We have fixed an issue that caused the Microsoft linker to emit
  warning `LNK4001`: "no object files specified; libraries used".

* We have fixed an incorrect overflow check in `string.to_int/2`,
  `string.to_uint`, `string.base_string_to_int/3` and
  `string.base_string_to_uint/3`.

* We have fixed a bug where `string.to_uint/2` and
  `string.base_string_to_uint/3` returned zero instead of failing
  when called with an empty input string.

* Many documentation fixes and improvements.

NEWS for Mercury 22.01.8
========================

This is a bug-fix release.

* [Mantis bug #565]. We have reverted a change that broke `mmake` in Mercury
  versions 22.01.6 and 22.01.7.

* We have fixed a problem that was causing the generation of the debugger
  documentation to fail on Cygwin.

* We have increased the C stack size for the compiler on 64-bit Cygwin systems,
  due to stack overflows occuring with the default size.

* We have fixed a bug in the debugger, which, in some rare circumstances, could
  cause it to print terms to the wrong stream.

NEWS for Mercury 22.01.7
========================

This is a bug-fix release.

* [Github issue #123]. We have fixed a problem that was causing compilation
  with GCC 13 to fail.

* We have renamed a macro used in the compiler to avoid a clash with
  the system headers in the MSYS2 UCRT64 environment.

* We have fixed a problem that was causing the generation of the debugger
  documentation to fail on Windows.

* We have fixed a problem where MSVC could not compile the C code generated for
  some tabled Mercury predicates. This was caused by the C code inadvertently
  making use of some GNU C extensions that MSVC does not support.

NEWS for Mercury 22.01.6
========================

This is a bug-fix release.

* We have fixed the implementations of transitive closure and reflexive
  transitive closure in the `digraph` module.

* We have a fixed a bug in `string.format` and related predicates where `int8`,
  `int16` and `int32` values were being incorrectly promoted to `int` and sign
  extended when one of the unsigned conversion specifiers was applied.

* [Github issue #116]. We have fixed a problem building programs with
  `--intermodule-optimization` where the compiler was searching for library
  files that were not installed unless the library was also built with
  `--intermodule-optimization` enabled.

* [Github issue #117]. We have fixed a bug where the compiler would silently
  fail when compiling a program that consists of a single source file and
  some of the required libraries are not available in the selected grade.

* The documentation of the following predicates in the `term_io` module has
  been fixed:

    - pred `quote_char/3`
    - pred `quote_atom/3`
    - pred `write_escaped_char/3`
    - pred `write_escaped_string/3`

  Their documentation said that they write to `stdout`, when in fact
  they write to the current text output stream. By default, this is `stdout`,
  but calls to `io.set_output_stream` may change this.

NEWS for Mercury 22.01.5
========================

This is a bug-fix release.

* We have fixed a bug that was causing invalid fact table file names
  to be written to dependency files.

* We have fixed a bug with the MLDS backend that was causing
  crashes with certain switches on strings.

* We have fixed a bug that was causing some transitive intermodule
  optimization interfaces to be silently ignored.

* We have fixed a bug where termination analysis could cause a compiler abort
  when invoked on some rarely-occurring predicate structures.

NEWS for Mercury 22.01.4
========================

This is a bug-fix release.

* We have fixed and clarified the behaviour of the following `string`
  module predicates when called on a string containing ill-formed code
  unit sequences:

    - pred `all_match/2`
    - pred `index_next_repl/5`
    - pred `unsafe_index_next_repl/5`
    - pred `prev_index_repl/5`
    - pred `unsafe_prev_index_repl/5`

* We have fixed a bug in the `getopt` and `getopt_io` modules where
  negating a `maybe_string` option would set its option table entry
  to an incorrect value.

* We have fixed an issue where flags specific to GCC were being
  passed to MSVC when building Mercury using MSVC.

NEWS for Mercury 22.01.3
========================

This is a bug-fix release.

* [Github issue #103]. We have disabled the use of some GCC optimizations
  that were causing segmentation faults in code compiled in the `asm_fast`
  grades with GCC versions 11 and 12 on x86_64 systems.

NEWS for Mercury 22.01.2
========================

This is a bug-fix release.

* [Mantis bug #558]. We have fixed a bug that was causing some of the
  manual pages to sometimes build incorrectly.

* [Mantis bug #560]. We have disabled the use of the `asm_fast*` grades on
  AArch64 when using GCC 9+ due to incompatibilities with position-independent
  code.

* We have fixed a bug that was causing assertion failures or segmentation
  violations in the Mercury runtime on AArch64 systems with versions of
  GCC before 10.

* [Github issue #102]. We have disabled the use of the GCC option
  `-Warray-bounds` for GCC version 12 and onwards. This is due to GCC
  emitting spurious warnings when that option is enabled.  (The use of
  that option was already disabled for GCC versions 9-11.)

NEWS for Mercury 22.01.1
========================

This is a bug-fix release.

* [Mantis bug #557]. We have fixed a bug in module qualification that was
  causing the compiler to fail without printing an error message.

NEWS for Mercury 22.01
======================

Changes that may break compatibility
------------------------------------

* We have removed `is` as a synonym for unification.

* We have reserved `=<`/2 as a type name.

* A term with a top-level functor `coerce/1` is now treated as a
  type conversion expression. To call a function named `coerce/1`,
  you can module qualify the name at the call site,
  or wrap parentheses around the name, e.g. `(coerce)(Arg)`.

* We have renamed the `lexer` and `parser` modules of the Mercury standard
  library to `mercury_term_lexer` and `mercury_term_parser` respectively.

* We have made slight changes to the names and/or the functionality
  of several predicates in the `getopt` and `getopt_io` modules.

* We have removed the legacy support for the Alpha architecture.

* We have dropped support for macOS 10.8 and earlier.

* We have removed the Erlang backend as it was unmaintained.

Changes to the Mercury standard library
---------------------------------------

### New module: `random.system_rng`

* This module provides an interface to a platform specific cryptographically
  secure random number generator that is seeded from the OS entropy pool.

### Changes to the `array` module

* The following obsolete predicates and functions have been removed:

    - func `bsearch/3`              (replacement: `binary_search/3`)
    - pred `bsearch/4`              (replacement: `binary_search/4`)
    - func `least_index/1`          (replacement: `min/1`)
    - func `greatest_index/1`       (replacement: `max/1`)

* The following predicate has been added:

    - pred `generate_foldl2/7`

### Changes to the `array2d` module

* The following predicates and functions have been added:

    - func `lookup/3`               (synonym for `Array ^ elem(R, C)`)
    - pred `lookup/4`               (synonym for `Array ^ elem(R, C)`)
    - func `unsafe_lookup/3`        (synonym for `Array ^ unsafe_elem(R, C)`)
    - pred `unsafe_lookup/4`        (synonym for `Array ^ unsafe_elem(R, C)`)

* The `lists/1` function now returns an empty list for a 0x0 array.

### Changes to the `assoc_list` module

* The following predicates and functions have been added:

    - func `common_subset/2`
    - pred `maybe_from_corresponding_lists/3`

### Changes to the `bag` module

* The following obsolete predicates and functions have been removed:

    - func `to_set_without_duplicates/1`    (replacement: func `to_set/1`)
    - pred `to_set_without_duplicates/2`    (replacement: func `to_set/1`)

### Changes to the `bitmap` module

* The following predicates and functions have been added:

    - func `get_bit/2`
    - func `get_bits/2`
    - func `get_byte/2`
    - pred `set_bit/4`
    - pred `set_bits/4`
    - pred `set_byte/4`
    - func `unsafe_get_bit/2`
    - func `unsafe_get_bits/2`
    - func `unsafe_get_byte/2`
    - pred `unsafe_set_bit/4`
    - pred `unsafe_set_bits/4`
    - pred `unsafe_set_byte/4`

### Changes to the `char` module

* The following predicates have been added:

    - pred `unsafe_base_digit_to_int/3`
    - pred `to_utf8_uint8/2`
    - pred `to_utf16_uint16/2`

* The following obsolete predicates and functions have been removed:

    - func `det_int_to_digit/1`     (replacement: `det_int_to_decimal_digit/1`)
    - pred `det_int_to_digit/2`     (replacement: `det_int_to_decimal_digit/2`)
    - pred `digit_to_int/2`         (replacement: `decimal_digit_to_int/2`)
    - pred `int_to_digit/2`         (replacement: `int_to_decimal_digit/2`)

### Changes to the `cord` module

* The following predicates have been added:

    - pred `foldl2/6`
    - pred `foldl3/8`

### Changes to the `dir` module

* The following predicate has been added:

    - pred `general_foldl2/8`

### Changes to the `getopt` module

* The following new predicates have been added:

    - pred `record_arguments/8`
    - pred `expand_file_specials/8`

* The following variants of the existing process_options predicate
  have been added:

    - pred `process_options_io/6`
    - pred `process_options_io/7`
    - pred `process_options_track_io/9`
    - pred `process_options_userdata/8`
    - pred `process_options_userdata_io/10`

    The ones whose names have an `_io` suffix do the same jobs as the
    corresponding predicates without the `_io` suffix, with the exception
    that they also have a pair of I/O state arguments that allow them
    to implement `file_special` options. This functionality used to be
    available only from the `getopt_io` module.

* The following predicates have had their argument types changed:

    - pred `process_options/6`
    - pred `process_options/7`
    - pred `process_options_track/7`

    All these predicates used to return error indications in the form of a
    simple string. They now return error indications using the existing
    structured type `option_error`, which can be converted into a string
    on demand.

* The following predicates have been deleted:

    - pred `process_options_se/6`
    - pred `process_options_se/7`
    - pred `process_options_track_se/7`

    Their functionality is now available from the predicates with the same name
    minus the `_se` suffix.

### Changes to the `getopt_io` module

* This module has been deprecated. For now, it exports the same functionality
  as the updated `getopt` module, but it is scheduled to be deleted after
  the next release.

### Changes to the `int` module

* The following functions have been added:

    - func `uint_to_lc_hex_string/2`    (synonym for `uint_to_hex_string/2`)
    - func `uint64_to_lc_hex_string/2`  (synonym for `uint64_to_hex_string/2`)

* The following obsolete predicates and functions have been removed:

    - pred `is/2`                   (replacement: `=`, i.e. unification)
    - func `legacy_left_shift/2`    (replacement: `<<`)
    - func `legacy_right_shift/2`   (replacement: `>>`)

### Changes to the `int32` module

* The following functions have been added:

    - func `cast_to_int8`
    - func `cast_from_int8`
    - func `cast_to_int16`
    - func `cast_from_int16`
    - func `cast_to_int64`
    - func `cast_from_int64`

### Changes to the `integer` module

* The following obsolete functions have been removed:

    - func `from_base_string/2`     (replacement: pred `from_base_string/3`)
    - func `from_string/2`          (replacement: pred `from_string/2`)
    - func `int/2`                  (replacement: `det_to_int/1`)

### Changes to the `io` module

* The following predicates have been added to this module:

    - pred `get_environment_var_map/3`
    - pred `read_binary_int8_unboxed/5`
    - pred `read_binary_uint8_unboxed/5`
    - pred `read_named_file_as_string/4`
    - pred `read_named_file_as_lines/4`
    - pred `write_line_cc/4`

* The following obsolete predicates have been removed:

    - pred `make_temp/3`            (replacement: `make_temp_file/3`)
    - pred `make_temp/5`            (replacement: `make_temp_file/5`)

* The following predicates have been marked as obsolete:

    - pred `see/4`                  (replacement: `prolog.see/4`)
    - pred `see_binary/4`           (replacement: `prolog.see_binary/4`)
    - pred `seen/2`                 (replacement: `prolog.seen/2`)
    - pred `seen_binary/2`          (replacement: `prolog.seen_binary/2`)
    - pred `tell/4`                 (replacement: `prolog.tell/4`)
    - pred `tell_binary/4`          (replacement: `prolog.tell_binary/4`)
    - pred `told/2`                 (replacement: `prolog.told/2`)
    - pred `told_binary/2`          (replacement: `prolog.told_binary/2`)

* The following predicate has been renamed:

    - pred `report_stats/2` to `report_standard_stats/2`.

### Changes to the `lexer` module

* This module has been renamed to `mercury_term_lexer`, to make
  name clashes between it and user-written modules less likely.

### Changes to the `list` module

* The following predicates have been added:

    - pred `delete_nth/3`
    - pred `foldl7/16`
    - pred `foldl8/18`
    - pred `foldl4_corresponding/11`

* The following obsolete predicate has been removed:

    - pred `takewhile/4`            (replacement: `take_while/4`)

### Changes to the `map` module

* The following predicates have been added to this module:

    - pred `foldl6/14`
    - pred `foldl6_values/14`
    - pred `foldr6/14`

### Changes to the `maybe` module

* The following predicates have been added to this module:

    - pred `foldl3_maybe/8`
    - pred `foldl4_maybe/10`
    - pred `foldl5_maybe/12`
    - pred `map_foldl4_maybe/11`
    - pred `map_foldl5_maybe/13`

### Changes to the `parser` module

* This module has been renamed to `mercury_term_parser`, to make
  name clashes between it and user-written modules less likely.

### Changes to the `prolog` module

* The following predicate has been added to this module:

    - pred `is/2`                   (moved here from the `int` module)
    - pred `see/4`                  (moved here from the `io` module)
    - pred `see_binary/4`           (moved here from the `io` module)
    - pred `seen/2`                 (moved here from the `io` module)
    - pred `seen_binary/2`          (moved here from the `io` module)
    - pred `tell/4`                 (moved here from the `io` module)
    - pred `tell_binary/4`          (moved here from the `io` module)
    - pred `told/2`                 (moved here from the `io` module)
    - pred `told_binary/2`          (moved here from the `io` module)

### Changes to the `random` module

* The following obsolete predicate has been removed:

    - pred `test/4`                 (replacement: none)

### Changes to the `std_util` module

* The following obsolete predicates and functions have been removed:

    - func `maybe_func/2`           (replacement: func `maybe.func_to_maybe/1`)
    - pred `maybe_pred/3`           (replacement: func `maybe.pred_to_maybe/1`)

### Changes to the `string` module

* The following functions have been added:

    - func `add_suffix/2`
    - func `split_into_lines/1`
    - pred `to_uint/2`
    - func `det_to_uint/1`
    - pred `base_string_to_uint/3`
    - func `det_base_string_to_uint/2`
    - func `uint_to_hex_string/1`
    - func `uint_to_uc_hex_string/1`
    - func `uint_to_octal_string/1`
    - func `uint64_to_hex_string/1`
    - func `uint64_to_uc_hex_string/1`
    - func `uint64_to_octal_string/1`

* The following function symbols have been added to the type `poly_type`:

    - `i8(int8)`
    - `i16(int16)`
    - `i32(int32)`
    - `i64(int64)`
    - `u8(uint8)`
    - `u16(uint16)`
    - `u32(uint32)`
    - `u64(uint64)`

  This allows predicates such as `string.format` and `io.format` to operate
  on values of not just the word sized integer types `int` and `uint`, but on
  sized versions of them as well.

### Changes to the `term` module

* The following obsolete predicates and functions have been removed:

    - func `var_id/1`               (replacement: `var_to_int/1`)

    - func `relabel_variable/3`     (replacement: `rename_var_in_term/4`)
    - pred `relabel_variable/4`     (replacement: `rename_var_in_term/4`)
    - func `relabel_variables/3`    (replacement: `rename_var_in_terms/4`)
    - pred `relabel_variables/4`    (replacement: `rename_var_in_terms/4`)

    - func `rename/3`               (replacement: `rename_var_in_term/4`)
    - pred `rename/4`               (replacement: `rename_var_in_term/4`)
    - func `rename_list/3`          (replacement: `rename_var_in_terms/4`)
    - pred `rename_list/4`          (replacement: `rename_var_in_terms/4`)

    - func `apply_renaming/3`       (replacement: `apply_renaming_in_term/3`)
    - pred `apply_renaming/3`       (replacement: `apply_renaming_in_term/3`)
    - func `apply_renaming_to_list/3`
                                    (replacement: `apply_renaming_in_terms/3`)
    - pred `apply_renaming_to_list/3`
                                    (replacement: `apply_renaming_in_terms/3`)

    - func `apply_variable_renaming/2`
                                    (replacement: `apply_renaming_in_term/3`)
    - pred `apply_variable_renaming/3`
                                    (replacement: `apply_renaming_in_term/3`)
    - func `apply_variable_renaming_to_list/2`
                                    (replacement: `apply_renaming_in_terms/3`)
    - pred `apply_variable_renaming_to_list/3`
                                    (replacement: `apply_renaming_in_terms/3`)

    - func `apply_variable_renaming_to_var/2`
                                    (replacement: `apply_renaming_in_var/3`)
    - pred `apply_variable_renaming_to_var/3`
                                    (replacement: `apply_renaming_in_var/3`)
    - func `apply_variable_renaming_to_vars/2`
                                    (replacement: `apply_renaming_in_vars/3`)
    - pred `apply_variable_renaming_to_vars/3`
                                    (replacement: `apply_renaming_in_vars/3`)

    - func `substitute/3`           (replacement: `substitute_var_in_term/4`)
    - pred `substitute/4`           (replacement: `substitute_var_in_term/4`)
    - func `substitute_list/3`      (replacement: `substitute_var_in_terms/4`)
    - pred `substitute_list/4`      (replacement: `substitute_var_in_terms/4`)

    - func `substitute_corresponding/3`
                        (replacement: `substitute_corresponding_in_term/4`)
    - pred `substitute_corresponding/4`
                        (replacement: `substitute_corresponding_in_term/4`)
    - func `substitute_corresponding_list/3`
                        (replacement: `substitute_corresponding_in_terms/4`)
    - pred `substitute_corresponding_list/4`
                        (replacement: `substitute_corresponding_in_terms/4`)

    - func `apply_substitution/2`
                        (replacement: `apply_substitution_in_term/3`)
    - pred `apply_substitution/3`
                        (replacement: `apply_substitution_in_term/3`)
    - func `apply_substitution_to_list/2`
                        (replacement: `apply_substitution_in_terms/3`)
    - pred `apply_substitution_to_list/3`
                        (replacement: `apply_substitution_in_terms/3`)

    - func `apply_rec_substitution/2`
                        (replacement: `apply_rec_substitution_in_term/3`)
    - pred `apply_rec_substitution/3`
                        (replacement: `apply_rec_substitution_in_term/3`)
    - func `apply_rec_substitution_to_list/2`
                        (replacement: `apply_rec_substitution_in_terms/3`)
    - pred `apply_rec_substitution_to_list/3`
                        (replacement: `apply_rec_substitution_in_terms/3`)

### Changes to the `thread` module

* The following predicate and functions have been added:

    - func `init_thread_options/0`
    - pred `set_min_stack_size/3`
    - pred `spawn_native/5`

### Changes to the `thread.mvar` module

* The following obsolete function has been removed:

    - func `init/1`                 (replacement: `impure_init/1`)

### Changes to the `thread.semaphore` module

* The following obsolete function has been removed:

    - func `init/1`                 (replacement: `impure_init/1`)

### Changes to the `time` module

* The following obsolete functions have been removed:

    - func `ctime/1`                (replacement: `localtime/4` and `asctime/1`)
    - func `localtime/1`            (replacement: `localtime/4`)
    - func `mktime/1`               (replacement: `mktime/4`)

### Changes to the `tree234` module

* The following predicates have been added to this module:

    - pred `foldl6/14`
    - pred `foldl6_values/14`
    - pred `foldr6/14`

### Changes to the `uint16` module

* The following functions have been added:

    - pred `from_uint/2`
    - func `det_from_uint/1`
    - func `cast_from_uint/1`
    - func `rotate_left/2`
    - func `rotate_right/2`
    - func `unchecked_rotate_left/2`
    - func `unchecked_rotate_right/2`
    - func `set_bit/2`
    - func `unchecked_set_bit/2`
    - func `clear_bit/2`
    - func `unchecked_clear_bit/2`
    - func `flip_bit/2`
    - func `unchecked_flip_bit/2`
    - func `bit_is_set/2`
    - func `unchecked_bit_is_set/2`
    - func `bit_is_clear/2`
    - func `unchecked_bit_is_clear/2`
    - func `cast_from_uint8/1`
    - func `cast_to_uint8/1`

### Changes to the `uint32` module

* The following functions have been added:

    - pred `from_uint/2`
    - func `det_from_uint/1`
    - func `rotate_left/2`
    - func `rotate_right/2`
    - func `unchecked_rotate_left/2`
    - func `unchecked_rotate_right/2`
    - func `set_bit/2`
    - func `unchecked_set_bit/2`
    - func `clear_bit/2`
    - func `unchecked_clear_bit/2`
    - func `flip_bit/2`
    - func `unchecked_flip_bit/2`
    - func `bit_is_set/2`
    - func `unchecked_bit_is_set/2`
    - func `bit_is_clear/2`
    - func `unchecked_bit_is_clear/2`
    - func `cast_from_uint8/1`
    - func `cast_to_uint8/1`
    - func `cast_from_uint16/1`
    - func `cast_to_uint16/1`

### Changes to the `uint64` module

* The following functions have been added:

    - func `cast_from_uint/1`
    - func `rotate_left/2`
    - func `rotate_right/2`
    - func `unchecked_rotate_left/2`
    - func `unchecked_rotate_right/2`
    - func `set_bit/2`
    - func `unchecked_set_bit/2`
    - func `clear_bit/2`
    - func `unchecked_clear_bit/2`
    - func `flip_bit/2`
    - func `unchecked_flip_bit/2`
    - func `bit_is_set/2`
    - func `unchecked_bit_is_set/2`
    - func `bit_is_clear/2`
    - func `unchecked_bit_is_clear/2`
    - func `cast_from_uint8/1`
    - func `cast_to_uint8/1`

### Changes to the `uint8` module

* The following functions have been added:

    - pred `from_uint/2`
    - func `det_from_uint/1`
    - func `cast_from_uint/1`
    - func `rotate_left/2`
    - func `rotate_right/2`
    - func `unchecked_rotate_left/2`
    - func `unchecked_rotate_right/2`
    - func `set_bit/2`
    - func `unchecked_set_bit/2`
    - func `clear_bit/2`
    - func `unchecked_clear_bit/2`
    - func `flip_bit/2`
    - func `unchecked_flip_bit/2`
    - func `bit_is_set/2`
    - func `unchecked_bit_is_set/2`
    - func `bit_is_clear/2`
    - func `unchecked_bit_is_clear/2`

### Changes to the `varset` module

* The following obsolete predicates have been removed:

    - pred `merge_subst/4`      (replacement: `merge_renaming/4`)
    - pred `merge_subst_without_names/4`
                                (replacement: `merge_renaming_without_names/4`)

* The following functions and predicates have been added:

    - func `unname_var/2`
    - pred `unname_var/3`
    - pred `undo_default_names/2`

Changes to the Mercury language
-------------------------------

* The type system now supports subtypes, which work in tandem with
  type conversion expressions ("coerce"). For example, the following
  defines a subtype `real_color` of a discriminated union type `color`:

        :- type color
            --->    rgb(float, float, float)
            ;       cmyk(float, float, float, float)
            ;       named(string).

        :- type real_color =< color
            --->    rgb(float, float, float)
            ;       cmyk(float, float, float, float).

  A term of type `real_color` can be converted to a term of type `color`
  with `coerce(Term)`. A term of type `color` can be converted to a term of
  type `real_color` if it has an appropriate inst. Subtypes share a common
  data representation with their base types, so the type conversions do not
  cost anything at runtime.

* Field names no longer need to be unique within a module.

* The compiler can implement tabling only when generating C code.
  When compiling a predicate that has a `pragma memo` specified for it
  in a non-C grade, it necessarily ignores the pragma, but normally
  it prints a warning about this fact. The compiler now supports
  a new attribute, `disable_warning_if_ignored`, that suppresses
  such warnings for a `pragma memo` if included in the pragma's
  attribute list, like this:

        :- pragma memo(predname/arity, [disable_warning_if_ignored])]).

* A `pragma foreign_proc` declaration can now include an attribute
  `may_not_export_body` that prevents its body (i.e. the foreign code)
  from being duplicated outside of the target file for that module
  by intermodule optimization. This is useful when the foreign code
  refers to types, functions, etc. that should be kept local to the
  target file of that module. Unlike the `may_not_duplicate` attribute,
  `may_not_export_body` does not prevent inlining of the foreign procedure
  into other procedures in the same module.

* Many pragmas contain a name/arity pair for specifying the predicate
  or function they apply to; an example is

        :- pragma inline(init/1).

  If the module in which this pragma occurs contains both
  a function `init/1` and a predicate `init/1`, then this pragma
  is ambiguous. Traditionally, the Mercury compiler applied such
  ambiguous pragma to both the function and the predicate.
  The programmers who wished the pragma to apply to only one of them
  had to rename the other.

  Now, pragmas that take a name/arity pair can specify whether they are
  intended to apply to a function or to a predicate by putting a `func()`
  or `pred()` wrapper around the name/arity pair, like this:

        :- pragma inline(func(init/1)).     % applies ONLY to func init/1.
        :- pragma inline(pred(init/1)).     % applies ONLY to pred init/1.

  This new syntax applies to all of the following kinds of pragmas:

        check_termination
        consider_used
        does_not_terminate
        fact_table
        inline
        loop_check
        memo
        minimal_model
        mode_check_clauses
        no_determinism_warning
        no_inline
        obsolete
        promise_equivalent_clauses
        promise_pure
        promise_semipure
        require_tail_recursion
        terminates
        type_spec

Changes to the Mercury compiler
-------------------------------

* If a command line first enables an optimization (say `opt1`), and then
  sets the optimization level to `N` with `-O<N>`, then the compiler will now
  keep `opt1` enabled even if `opt1` is not normally enabled at optimization
  level `N`.

* Due to a bug fix, the `--warn-unused-imports` option is now stricter in
  warning about modules that are imported in the interface section but are
  not used in the interface section.

* We have fixed parsing of reverse implication goals (A <= B).

* By default, the compiler now checks some aspects of a module semantics
  when generating the .int and .int2 interface files for that module.
  (For example, it generates error messages for references to undefined
  types, insts and modes.) This new behavior can be switched off for now
  with the new option `--no-halt-at-invalid-interface`. This new option
  replaces the old `--no-print-errors-warnings-when-generating-interface`
  option, but once any problems caused by the new approach have been
  ironed out, we intend to delete the `--halt-at-invalid-interface`
  option as well.

* In an earlier release, we extended the syntax of `:- inst` declarations
  to allow programmers to specify which type constructor's values the inst
  is meant for. At that time, these functioned only as documentation,
  but the compiler now reports error messages for situations in which
  an inst that was declared to be intended for values of one type constructor
  is applied to values of another type constructor.

* The new option `--output-stdlib-grades` outputs the grades in which
  the Mercury standard library is available with this compiler.

* By default, the compiler now warns if the module being compiled has a name
  that shadows that of Mercury standard library module. The warning can be
  disabled using the new option `--no-warn-stdlib-shadowing`.

* The new options `--output-java-class-dir` and `--output-java-class-directory`
  are now supported as synonyms for `--output-class-dir`.

* The new option `--halt-at-warn-make-interface` causes the compiler to
  treat all warnings as if they were errors when generating interface files.

* The new option `--halt-at-warn-make-opt` causes the compiler to
  treat all warnings as if they were errors when generating optimization files.

* The new option `--warn-potentially-ambiguous-pragma` causes the compiler to
  generate a warning for all pragmas that include a name/arity pair,
  but lack a `func()` or `pred()` wrapper around it to indicate whether they
  are intended to apply to a function or to a predicate.

Portability improvements
------------------------

* We have ported Mercury to Linux AArch64 (ARM64) systems.

* The `tools/configure_mingw_cross` script has been replaced by
  `tools/configure_cross`. It now supports aarch64-linux-gnu and
  aarch64-linux-musl as targets (i.e. Linux on aarch64 with GNU or
  musl C libraries).

Changes to the Mercury debugger
-------------------------------

* The `list` command may now call an external command to print source listings;
  the command is set using `list_cmd`.  For example, the command could
  produce syntax highlighted source listings.

* We have removed support for browsing terms as XML (`browse --xml`)
  as it was unmaintained and did not work any more. The `browse --web`
  command provides an alternative method for interactively exploring a term.

For news about earlier versions, see the HISTORY file.
