Release v2.0.0 [How Not to Be Seen]

[evhub]

Coconut v2 is here! See Coconut's documentation for more information on all of the features listed below.

Breaking changes:

• Coconut 2.0 pattern-matching changes #605: Coconut pattern-matching is now fully unified with Python 3.10 pattern-matching: pattern-matching always works the same way regardless of where it is used, always uses Python 3.10 rules, but also always supports all additional Coconut pattern-matching features. Some implications of this:
  • Coconut now fully supports class patterns everywhere, including in pattern-matching function definition and destructuring assignment.
  • As a result, x is int type-checking syntax is now deprecated in favor of using the int(x) class pattern. For cases where there is now rewriting as a class pattern, x `isinstance` int syntax is also supported.
  • Pattern-matching for dictionaries has been changed so that {"a": a} now matches a dictionary with at least "a" as a key rather than exactly "a" as its only key to be consistent with Python 3.10. Coconut will warn if such syntax is detected and suggest the explicit {"a": a, **_} or {"a": a, **{}} syntax instead.
• data types should not add and multiply like tuples #639: Coconut data types no longer support adding or multiplying them like tuples unless explicitly added via __add__/__mul__ methods.
• fmap over a dict should map over the items, not starmap #623: fmap over a Mapping (e.g. dict) now does a normal map instead of a starmap. Thus, you'll need to do fmap$(def ((k, v)) -> (new_k, new_v)) instead of fmap$((k, v) -> (new_k, new_v)). Old behavior can also be recovered with fmap$(starmap_over_mappings=True).
• Add getitem and change iter_getitem operator function notations #615: ($[]) spelling for the iterator slicing operator function has been removed in favor of .$[] and the normal getitem operator has been added as .[].
• Change precedence of function composition #613: Precedence of the function composition operator .. has been lowered such that f x .. g y is now equivalent to (f x) .. (g y) rather than ((f x) .. g) y.
• Change initializer to initial in scan signature to match reduce #635: initializer keyword argument in scan changed to initial to match the function signature of reduce.

New language features:

• Add multidimensional array literals #628, Allow overriding multidimensional array concatenation #670: New multidimensional array literal and concatenation syntax! Concatenate two arrays with [a ; a], write out 2D array literals as [1, 2;; 3, 4], with the number of semicolons denoting the axis from the end on which to concatenate.
• In addition to implicit lambdas, also add implicit partial application for operator functions #258, Support infix functions in implicit partials #669: New syntax for partially applying operator functions: (.+1), (a+.), (.<|x), including support for custom operators as (. plus x).
• Add Tuple shorthand in type hints #663: Better syntax for typing tuples: instead of x: typing.Tuple[int, str], just: x: (int; str).
• Add pattern-matching for loops #633: New pattern-matching for loops, allowing for arbitrary destructuring pattern-matching in for loops.
• Anonymous named tuples #622, Make anonymous namedtuples pickleable #650: New anonymous named tuples for giving names to fields in temporary tuples. Just: (a=1, b=2).
• Allow converting keyword arguments to positional arguments in partials #626: New syntax for using partial application to convert a keyword argument into a positional argument. Just: func$(kwd_arg=?).
• Add combinators (ident, flip, const, S, S') #612: Combinators! Use lift to "lift" a function up so that its arguments become unary functions. Also: ident, flip, const, of.
• Add built-ins from more_itertools #616, Add collectby built-in #620: New all_equal and collectby built-ins for working with iterables.
• Add a way to map over asynchronous iterables #124: fmap now supports asynchronous iterators.
• Use == instead of = for equality checking in pattern-matching #365 (thanks @ArneBachmann!): Equality checking with =<expr> has been deprecated in favor of ==<expr>; the former syntax will now raise an error in --strict mode.
• Add strict class patterns #648: Class patterns now support a strict .attr=<match> syntax that raises an error if the attr isn't present rather than failing the match.
• Support linear sequence search patterns #641: Iterable destructuring patterns now support a substantially wider array of allowable destructuring constructs (e.g. [1] + x + [2] + y + [3]).
• Support PEP 642 alternative pattern-matching syntax #603: New as x (to explicitly bind a variable) and is x (to do an identity check) pattern-matching constructs.
• Discussion: Conditional assignment #434 (thanks @ArneBachmann!): Conditional assignment using pattern-matching; infix patterns have been improved to support a `pred` or b = <expr> syntax that binds to a if pred and b otherwise.
• Allow overriding multidimensional array concatenation #670: jax support in fmap and multidimensional array literal/concatenation.
• Add tuple operator function #617, Add (raise) operator function #647: New comma operator function (,) for joining arguments into a tuple and new (raise) operator function for raising an exception.
• Universalize matrix multiplication #625: Matrix multiplication operator @ now supported on all Python versions.
• Universalize zero-argument super #649 (thanks @hlizard!): Zero-argument super() now supported on all Python versions.
• Add typing_extensions automatic backporting #664: Coconut will now automatically backport typing imports into typing_extensions imports when necessary.
• Allow chaining assignment expressions with fewer parentheses. #490 (thanks @pavelbraginskiy!): := assignment expressions can now be chained without parentheses.
• Support f-strings in string patterns #640: f-strings now supported in pattern-matching string patterns.

New compiler features:

• Substantially improve error messages #632: Substantially improved syntax error messages with much finer-grained identification of the error location.
• Write xontrib to allow Coconut in xonsh #636: Coconut can now be used as a xontrib in the xonsh shell to enable Coconut syntax.
• Compatibility with papermill #658: Coconut now supports papermill.
• Improve interpreter auto-completion #575: Better interpreter auto-completing.
• Add coconut[kernel] installation option for a lightweight Coconut + Jupyter kernel dependencies install #629 (thanks @tbsexton!): New coconut[kernel] installation option for installing only lightweight Jupyter kernel dependencies compared to the full support offered by coconut[jupyter].
• Add global-state-free convenience API #646: Better coconut.convenience API.

Bugfixes:

• coconut -w errors with "NameError: name 'args' is not defined" #638 (thanks @ivanmkc!): coconut --watch for watching files for changes to be recompiled fixed.
• Ipython and Jupyter unexpected keyword argument cell_id #657 (thanks @tbsexton!): Jupyter kernel compatibility with new Jupyter/IPython versions fixed.
• Add built-ins from more_itertools #616: Iterator slicing no longer exhausts the entire iterator except when strictly necessary.
• Register numpy arrays as a collections.abc.Sequence #631: Fixed pattern-matching on numpy arrays by registering them as Sequences.
• ABC.coco compiled to abc.py not ABC.py #656 (thanks @hlizard!): Compilation on Windows should no longer convert names of compiled files to lowercase.
• Argument expansion erroneusly detected as "not positional" #627 (thanks @fakuivan!): Support for starred function arguments before positional function arguments.
• Allow defining fmap for different input types with pattern matching #653 (thanks @fakuivan!): Fixed dotted names in class/data patterns.
• coconut.exceptions.CoconutInternalException: invalid string start location in f string #655 (thanks @hlizard!): Certain complex f-strings no longer trigger internal Coconut exceptions.
• Coconut REPL crashes when importing some functions with mixed typed and untyped arguments. #667 (thanks @tom-a-horrocks!): Rare interpreter crashes fixed.

[evhub]

TODO: Once Coconut v2 is released, Coconut should be added to xonsh's list of xontribs.