Author: lwall Date: 2010-04-20 02:23:07 +0200 (Tue, 20 Apr 2010) New Revision: 30412

Modified: docs/Perl6/Spec/S02-bits.pod Log: [S02] define the term 'now' define math on instants and durations Modified: docs/Perl6/Spec/S02-bits.pod =================================================================== --- docs/Perl6/Spec/S02-bits.pod 2010-04-19 23:31:02 UTC (rev 30411) +++ docs/Perl6/Spec/S02-bits.pod 2010-04-20 00:23:07 UTC (rev 30412) @@ -13,8 +13,8 @@ Created: 10 Aug 2004 - Last Modified: 10 Apr 2010 - Version: 213 + Last Modified: 19 Apr 2010 + Version: 214 This document summarizes Apocalypse 2, which covers small-scale lexical items and typological issues. (These Synopses also contain @@ -1291,7 +1291,7 @@ C<Duration> values are still just atomic time without any cultural deformations; in particular, the C<Duration> formed of by subtracting C<Instant::Epoch::POSIX> from the current instant will contain more -seconds than the current POSIX time due to POSIX's abysmal ignorance +seconds than the current POSIX C<time()> due to POSIX's abysmal ignorance of leap seconds. This is not the fault of the universe, which is not fooled (neglecting relativistic considerations). C<Instant>s and C<Duration>s are always linear atomic seconds. Systems which cannot @@ -1314,6 +1314,30 @@ Or whatever. C<Instant> is opaque, so we can swap implementations in and out without user-visible consequences. +The term C<now> returns the current time as an C<Instant>. As with the +C<rand> and C<self> terms, it is not a function, so don't put parens after it. +It also never looks for arguments, so the next token should be an operator +or terminator. + + now + 300 # the instant five minutes from now + +Basic math operations are defined for instants and durations such +that the sum of an instant and a duration is always an instant, +while the difference of two instants is always a duration. Math on +instants may only be done with durations (or numbers that will +be taken as durations, as above); you may not add two instants. + + $instant + $instant # WRONG + $instant - $instant # ok, returns a duration + $instant + $duration # ok, returnas an instant + +Durations allow additive operations with other durations, and allow +any numeric operation with a number as the other argument: + + $duration * $duration # WRONG, durations aren't geometric + $duration * 2 # ok, a duration twice as long + 2 * $duration # same + These types do (at least) the following roles: Class Roles