preliminary version 0.5 release notes

ideas/Rel0.5.md

@@ -0,0 +1,176 @@
+Curv Changes since Release 0.4
+==============================
+There are multiple language changes, with deprecation warnings for old
+syntax. You should fix deprecation warnings now if you have old Curv code,
+because the old syntax will be removed in a future release. By default,
+deprecation warnings are throttled. Use `curv -v` to see all warnings.
+Features marked experimental are unstable, subject to change.
+
+Platform/Build Support
+----------------------
+Curv 0.5 includes a prebuilt AppImage for Linux.
+* @ComFreek -- Windows port.
+* @zeeyang: automated MacOS build (using github actions)
+* @A-G-D: automated AppImage build for Linux (using github actions)
+* Apple Silicon support on Macintosh.
+* AMD GPUs supported on Linux using AMD Mesa 19.x driver.
+* documented/tested exporting images on a headless Linux server.
+* `make upgrade` command
+
+File Import/Export
+------------------
+* @Xiaoyuew -- Faster mesh export (multi-threaded, multi-core).
+* @zeeyang: add `jgpu` export file format (GPU program as JSON)
+* @zeeyang: add `GLTF` export file format
+* @zeeyang: remove `curvc` (no longer being built)
+* `curv dirname` reads a directory as a Curv program (directory format)
+* JSON export no longer tries hard to distinguish JSON from non-JSON data.
+  Non-JSON data is now exported as a string.
+  `#foo` exports as `"foo"`. `sin` exports as `"<function sin>"`.
+
+Command Line
+------------
+* @A-G-D: filename now optional in `curv -le`, default is `new.curv`
+* Configuration file `~/.config/curv` contains defaults for -O options,
+  is a Curv source file, a record containing {viewer,export} fields.
+  See `docs/Config.rst`
+* All -O option values are now specified as Curv expressions.
+  Symbols used in -O options: -Ocolouring=#vertex or -Ocolouring=#face
+* rename -Ocolour= to -Ocolouring=
+* `--depr=` option controls deprecation warnings
+
+REPL
+----
+* supports := (assignment) statement
+* fully supports generator expressions
+* `help` in REPL is extremely experimental, only partially implemented
+* see `docs/REPL.rst`
+
+Rendering in Viewer Window
+--------------------------
+* @zeeyang: improved raymarching (backup if overstep due to bad SDF)
+* There are configurable render parameters. For a list, use `curv --help`.
+  * You can set them on the command line using `-Oname=value`.
+    What's new: `value` is an arbitrary Curv expression.
+  * You can set them in the config file, in the `viewer` section. [new]
+  * You can set them in a shape value by manually adding a `render` field
+    to the shape structure. [new, experimental]
+* new render parameters:
+  * ray_max_iter, ray_max_depth: bug #78 [experimental]
+  * `shader` -- lighting & shadow function for object surface [experimental]
+
+Shape Library
+-------------
+* @lf94: add `lib.builder` with `snowman` example [experimental]
+* @lf94: add `soroban` example
+* @zeeyang: add 2D `polyline` primitive
+* @zeeyang: add `repeat_finite` primitive
+* `capped_cone`
+* fix `show_axes` to preserve the bounding box
+* generalized `polygon` primitive (can be non-convex, self-intersecting)
+* lib.noise [experimental]
+* `a >> into union [b, c]` means `union [a, b, c]`
+
+Compiler and Interpreter
+------------------------
+* general tail call optimization
+* better compile/runtime error messages
+* function names in stack traces
+* SubCurv enhancements (more things that compile to GLSL shader language):
+  * numeric matrix data types: 2x2, 3x3, 4x4
+  * matrix multiplication (`dot`)
+  * boolean vector types: bool2, bool3, bool4, bool32
+  * boolean vector operations: and, or, xor, not
+  * boolean matrix types: bool2x32, bool3x32, bool4x32
+  * better support for parametric variables
+* add `docs/Implementation` (source code structure, lang. implementation)
+
+Curv Language
+-------------
+* Quoted identifiers: `'foo bar'` is an identifier with an embedded space.
+  `'if'` is an identifier, not a reserved word. `'_` is an escape sequence
+  representing a literal `'` within a quoted identifier.
+* Numbers
+  * number patterns like `42` or `-0.5`
+  * `sign` function returns -1, 0 or 1
+  * `sum` added to SubCurv
+* Lists
+  * `a++b` infix list catenation operator
+  * deprecate `(a,b,c)` list syntax; use `[a,b,c]` instead
+* A string like `"abc"` is now a list of characters.
+  Lists are heterogenous, so `"abc" ++ [1,2,3]` is a list of 6 elements.
+  * `#"a"` is a character literal, and works as a pattern.
+  * `is_char x` is true if `x` is a character value.
+  * `char` converts an integer or list of integers to a character or string.
+  * `ucode` converts a character or string to an integer or list of integers.
+  * `encode` removed, replaced by `ucode`.
+  * `decode` removed, replaced by `char`.
+  * `string` converts an arbitrary value to a string.
+  * new escape sequences in string literals: `$_` -> `$` and `"_` -> `"`
+* Symbols are abstract named values. They replace some uses of strings, but
+  symbols are scalars, not lists. They replace 'enum' values in some languages.
+  * #foo or #'hello world' is a symbol literal, which works as a pattern.
+  * `symbol` function constructs symbol from string
+  * `is_symbol` predicate.
+  * true, false, null are now just aliases for #true, #false, #null
+  * JSON export exports #true, #false, #null as JSON true, false, null.
+  * Remove `is_null` predicate (breaking change).
+* Data structure indexing
+  * `a.[i]` is new array indexing syntax. `a[i]` is deprecated.
+  * `r.[#foo]` is same as `r.foo`. Syntax r."foo" is deprecated.
+  * `a.foo.[i] := ...` assignment statements
+  * multi-dimensional array slicing using `a.[indexlist1,indexlist2]`
+  * generalized index values (aka lenses, experimental):
+    * `a.[i]` indexes a data structure with index value `i`
+    * integers are index values (they index lists)
+    * symbols are index values (they index records)
+    * `a.[[i1,i2,i3]]` yields `[a.[i1],a.[i2],a.[i3]]`
+    * `a.[this] yields `a`
+    * `a.[tpath[i1,i2]]` yields `a.[i1].[i2]`
+    * `a.[i1,i2]` is a multidimensional array slice,
+      short for `a.[tslice[i1,i2]]`.
+    * `amend index newelem tree` is pure functional update,
+      like `tree.[index]:=newelem` without the side effect.
+* Functions:
+  * `is_fun` deprecated, replaced by `is_func` and `is_primitive_func`
+  * `error` is a function value (previously was magic syntax)
+  * `id` -- identity function
+  * `identity` renamed to `idmatrix`
+  * `compose` is generalized to work correctly on partial functions
+* Boolean array operators.
+  * SubCurv supports new types Bool32, Bool[2-4], Bool[2-4]x32
+  * experimental boolean array operations (also in SubCurv):
+    * float_to_bool32, bool32_to_float
+    * nat_to_bool32 (in SubCurv, argument must be a constant)
+    * bool32_to_nat (not in SubCurv)
+    * bool32_sum, bool32_product
+    * lshift, rshift
+  * vectorized boolean `not` function; unary `!` operator is deprecated
+  * vectorized boolean reduction functions `and`, `or`, `xor`
+  * vectorized: <, <=, >, >=, bit
+  * `select` [experimental]
+* `parametric` records have a `call` field that reruns the constructor
+  with different parameter values. The result is another parametric record,
+  also with a `call` field.
+* `test` definitions, for unit tests in a module, or anywhere else
+* `sc_test` statement, for unit testing SubCurv [experimental]
+* `assert_error` statement, for writing unit tests
+* comma separated definition lists in `let ...` and `{...}`.
+  Previously only `;` was allowed as separator.
+* in a statement context, () and (a,b,c) are generators.
+* `where` is deprecated, use `let` instead.
+* in a dynamic record literal, [#a,1] is equivalent to a:1, both expressions
+* `locative!func1!func2` is a statement, mutates a local variable by
+  applying one or more functions to the contents.
+* deprecate "foo":expr, in expression or pattern context.
+* `until` clause for early exit from a `for` loop
+* `var` definitions are deprecated, use `local` definitions instead.
+* `local <definition>` is a generalized local definition, with sequential
+  (not recursive) scope. Legal in any imperative context: `do` expression,
+  compound statement, list constructor, dynamic record constructor.
+* Only definitions are permitted in the head of a `let` or in a module
+  (not actions). Use `test` definitions to add unit tests to a module.
+* Remove 'generalized do'. Only `do` expressions are supported.
+* fewer levels of operator precedence:
+  * unite Power with Unary; not a breaking change; grammar becomes more liberal.
+  * unite Relation with Range, breaking change, parse error for `1..3==[1,2,3]`