[fpc-devel] Closures via interfaces

Vasiliy Kevroletin kevroletin at gmail.com
Sun May 26 12:12:47 CEST 2013

Hi all,

About 2 months ago there was a big discussion about closures(thread 
"Delphi anonymous methods"). After this discussion I started work on 
Delhi-like closures for fpc. I am far from finish and current 
implementation is not perfect. But I already have positive results: it's 
possible to declare and use anonymous functions. After few changes 
closures will be able to capture variables. I created mantis#24481 to 
handle this work. Everyone who is interested in closures and good in 
compiler is welcome into mantis. I would be happy if someone looked into 
changes and said few words.

I described details of proposed and partly implemented approach in 
mantis. This is Delphi's approach. Some people call it "closures via 
interfaces". In slightly modified way it will allow to capture variables 
by value (which was requested in previous discussion). I like this 
approach because it's simple: it doesn't require to change codegenerator 
or rtl. On the other hand for each closure it creates new interface. And 
almost for each closure it creates new class. As a result: space 
overhead because of virtual tables and rtti.

My question to community is: what do you think about proposed 
implementation? Are there arguments for another approach?

Vasiliy K.

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