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chromatic (983)

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Sunday April 04, 2010
11:42 PM

Perl 6 Design Minutes for 31 March 2010

[ #40296 ]

The Perl 6 design team met by phone on 31 March 2010. Larry, Allison, Patrick, Will, and chromatic attended.


  • in SpecLand, made it clear that the brackets in pairs are not related to subscripts, but follow the corresponding fatarrow semantics
  • in particular, name extenders are just strings or list of strings, properly indicated by : or :() in most cases (this includes all operator names).
  • we now forbid name extension using the :{} keyless adverbial syntax
  • we don't need that because name extensions are really only supposed to use values, not closures
  • if we really, really, need to supply a closure as part of a name extension, we can put it in parens, as in :({}).
  • we can use that notation for supplying a closure as a first argument to a method without requiring a space between the colon and the curly, as in .map:{...}
  • people keep writing that and expecting it to work, so I thought it would be good to make it work
  • the colon is still require before the curlies, or it's a hash subscript
  • we now capitalize the Junction type again because I couldn't get people to stop capitalizing it
  • also, the native aspect of junctions is not their most salient difference from normal types
  • conjectured an Each type that autothreads lists like junctions, but is serial and lazy, and is used for its values in list context, not boolean context
  • in S05, did much cleanup of cursor semantics to reflect what STD and Rakudo actually do these days
  • retargeted the <&foo> regex assertion form to explicitly call a routine, just like <.foo> always calls a method
  • a bare <foo> assertion now prefers to call a lexical function if visible, or calls as a method in current grammar if not
  • this is a compile-time distinction, not a fallback at run time
  • in code hacking, continued debugging of the backtracking transactions I added last week
  • gimme5 now sets the correct xact on || alternations
  • deleted more of the transactions that are no longer needed when building match results that are no longer hypothetical
  • a LazyMap now always passes through the first result regardless of its associated commit transaction state
  • that's because the first cursor in a lazy list always represents the current match hypothesis, not a future hypothesis that needs pruning
  • STD now parses to the new specs regarding name extensions not including :{}
  • now allow colon form of method arguments to omit the space if the next char is a left curly, which is what people seem to expect anyway
  • note that this makes the closure the first argument, not the only argument
  • STD now gives more useful error messages when user says things like 'if' as a function call (if(...) {...}), or a statement control like 'given' where one isn't expected ($x = given {...})
  • STD now properly objects to unrecognized internal regex modifiers such as :has
  • improved the message on adverbs with empty angles (:foo<>) to list some better options
  • the problem arises when people think that the angles produce a null string, when in fact they produce a Nil list
  • other malformed pairs are also better diagnosed, such as :! not followed by an identifier, or pairs with duplicate arguments
  • added a new rule that traps all warnings and errors
  • STD now uses suppose in place of custom try blocks in diagnosing such things as two terms in a row, or unexpected infixes
  • also uses suppose to soften the warning about backtick-less embedded comments by not complaining if the supposed comment eats the whole line anyway
  • put in some code to de-dup identical warnings
  • STD now includes the signature's return type (after -->) in the check for redundant 'of' types
  • did various tiny speed tweaks, fossil removals
  • started playing with how to mark sink context and pure operations
  • split out from viv so that it can be used by other STD-based AST builders
  • this is in preparation for propagating attributes up and down the AST such as sink context and purity
  • eventually this will result in "Useless use of" messages where appropriate, not to mention the ability to do constant folding


  • worked on the compact_pool() function
  • split it into a series of smaller functions
  • it could use more work, but it's an improvement
  • found one possible bug
  • worked on some documentation, especially for PMC attributes


  • reviewed some patches to add variable handling in regexes
  • they need some changes, but the overall concept is good
  • reviewed a few other messages
  • most of my time is going toward my family
  • hope to get more time to be more active in the next couple of days, but I can't promise that yet


  • talked to Jonathan about Rakudo Star priorities
  • he's very pleased with the memory fixes
  • the next thing on his list is getting good line numbers in reported errors
  • closing tickets
  • working to get rid of the last recursive Makefile
  • may wait until after the new release, when we remove a lot of deprecated things
  • practicing my NQP skills by working on Tcl again


  • worked on the Rakudo memory problems
  • Vasily and I fixed the big memory use problem
  • still some performance tuning to do there
  • wrote up tasklists for two other important performance pieces
  • will work on line numbers after we get performance back
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