Author: ruoso Date: 2009-09-20 18:56:07 +0200 (Sun, 20 Sep 2009) New Revision: 28325
Added: docs/Perl6/Spec/S08-capture.pod Log: [spec/S08] started writing the introduction; Added: docs/Perl6/Spec/S08-capture.pod =================================================================== --- docs/Perl6/Spec/S08-capture.pod (rev 0) +++ docs/Perl6/Spec/S08-capture.pod 2009-09-20 16:56:07 UTC (rev 28325) @@ -0,0 +1,61 @@ + +=encoding utf8 + +=head1 TITLE + +Synopsis 8: Capture and Parcel + +=head1 AUTHORS + + Daniel Ruoso <dan...@ruoso.com> + +=head1 VERSION + + Created: 20 Sep 2009 + + Last Modified: 20 Sep 2009 + Version: 1 + +=head1 Introduction + +Unlike most programming languages, the data structure that is used to +send the parameters into a routine invocation (be it a method or a +sub) is exposed to the language as a built-in type like any +other. This represents a very important aspect of the Perl 6 runtime +requirements. + +Additionally to the fact that this data structure is visible in the +language type system, it is not assumed that the capture is a native +type, which means that the internal representation of the data is +subject to change. The only thing the runtime can assume is the API +described here. + +Of course the runtime can cheat whenever it knows the capture is +implemented by its own internal data structure for optimization +purposes, but it should allow the use of foreign types when invoking a +routine, as long as it says true to .^does(Capture). + +Captures and Parcels are also the basis for the multidimensionality of +lists in Perl 6. Unlike Perl 5, no flattening happens unless it's +explicitly required by the user, which is done by enforcing the List +context. If you use the scalar context the dimensionality should be +preserved. + +In addition to the List and Scalar context, there's also a special +context, which is, in a simplified way, called "Capture context", but +it actually means "deferred context", in a way that the Capture or +Parcel is kept as-is while they are manipulated in the code. This is +usefull to avoid unwanted flattening as well as avoiding the DWIMmy +features that might change the capture's behavior. + +This is the main point on why Capture and Parcel replace Perl 5 +references, they allow you to send data untouched from one place to +another. The second reason is that as in Perl 6 everything is an +object, there isn't really "pass-by-value" anymore, you're always +sending a reference, Captures and Parcels simply carry other objects +without enforcing any context on them. + +=head1 Additions + +Please post errors and feedback to perl6-language. If you are making +a general laundry list, please separate messages by topic.
