2023-01-12: Fuzion January Update

Hi,

In December, Fuzion improvements focused on the standard library and language improvements for covariance. Here is what has happened in detail:

• General
  • Two talks about Fuzion were accepted for FOSDEM on 4th and 5th of February: Algebraic Effects and Types as First-Class Features in the Fuzion Language and Fuzion: Mapping Java's Features to Simpler Mechanisms. We are looking forward to an in-person event after such a long time!
  • Wael Youssfi has finished his internship working on file I/O effects for Fuzion's base library. Big thanks for his contributions and all the best wishes for the future!
• Fuzion language

  • Support for covariant feature redefinition:

    a.this.type can now be used to refer to the type of an outer feature a. This can be used, e.g., to ensure that an argument or result of a feature has the same type as the target. E.g., numeric.infix + can require the argument and result to be of type numeric.this.type such that in a redefinition i32.infix + requires an argument of pf type i32 and produces a result of the same type.

  • Modifiers synchronized, const and leaf or no longer supported (but are still reserved keywords).
  • Added modifier fixed for features that should not be inherited by children of the outer feature.
  • A type parameter T with constraint c is now declared using T type : c which is in sync with the syntax for feature inheritance x : c is ....
• base library
  • infix ⋃ and infix ⋂ are now used for union and intersection instead of ∪ and ∩.
  • unit.type.monoid was added.
  • file.io now supports seek and file_position. exists was replaced by stats/lstats.
  • String now supports find_last, to_valid_utf8, fields_func, cut.
  • Indices in strings are now usually byte indices in the utf8-encoding, e.g., String.substring and String.split now use utf8-byte indices as arguments. Features working on codepoints were renamed for clarity: pad_start as pad_codepoint_start and substring_codepoint.
  • list now has features prepend_to_all and intersperse, no longer supports forceHead.
  • outcome now is a monad such that verbose match-statements can be replaced by concise calls to bind.
• fz tool
  • C back-end now uses -Wall -Werror by default.
• fzdocs tool
  • Now detects sample code in comments and makes it runnable in the browser.
• fuzion-lang.dev website
  • improved layout for small devices like smartphones.
  • Added design page for covariance and update page on casts for dynamic / ref types.

Cheers,

--Fridtjof.