Perl 6 Design Minutes for 31 March 2010

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

Larry:

• 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 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 Actions.pm 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

Allison:

• 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

Patrick:

• 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

Will:

• 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

c:

• 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

Syndicated 2010-04-05 04:42:21 from pudge