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implement "continue" and "break" with Xbase [message #1547643]

Mon, 05 January 2015 15:04

Lorenzo Bettini

Messages: 1812
Registered: July 2009
Location: Firenze, Italy

Senior Member

Hi

this is still related to the Xbase DSL I'm working on that should
reflect Java statements.

I'm implementing "continue" and "break"; I noted that under certain
conditions a basic for loop is translated into a Java while statement,
thus I'm customizing the Xbase compiler to deal with that.

From what I understand I should also customize the
DefaultEarlyExitComputer to check for dead code.

I have two doubts:

- does the use case of IEarlyExitComputer also consider cases for
branching statements like continue and break or is it used only for
statements that make the whole current method exit? From the comment in
the code I'd be tempted to say that it can't be used for branching
statements
- IEarlyExitComputer$ExitPoint has a protected constructor, which makes
it not instantiatable in a custom DefaultEarlyExitComputer; does that
mean that IEarlyExitComputer is not meant to be customized?

thanks in advance
Lorenzo

--
Lorenzo Bettini, PhD in Computer Science, DI, Univ. Torino
HOME: http://www.lorenzobettini.it
Xtext Book:
http://www.packtpub.com/implementing-domain-specific-languages-with-xtext-and-xtend/book

HOME: http://www.lorenzobettini.it
TDD Book: https://leanpub.com/tdd-buildautomation-ci
Xtext Book: https://www.packtpub.com/application-development/implementing-domain-specific-languages-xtext-and-xtend-second-edition

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Re: implement "continue" and "break" with Xbase [message #1548953 is a reply to message #1547643]

Tue, 06 January 2015 08:28

Sebastian Zarnekow

Messages: 3118
Registered: July 2009

Senior Member

Hi Lorenzo,

the protected constructor is an oversight. This will be changed for 2.8.
The early exit computer is used to detect code that will not be
executed. Since there is no break / continue in Xbase, there is no
special kind of ExitPoint for those. You may want to create a subtype of
ExitPoint to implement that. In that sense, the early exit computer does
consider branching, but it was not necessary to add the logic for jump /
branch expressions. You may want to look into
EarlyExitValidator.checkDeadCode(XIfExpression) to see how that is
generally done wrt to special expressions and branching.

Best,
Sebastian
--
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