<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div><div>On Aug 11, 2011, at 3:04 PM, Jordy Rose wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><span class="Apple-style-span" style="border-collapse: separate; font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; ">I'm curious what the motivation was for choosing to store the symbols as Base -> [list of dependents] instead of Dependent -> Base. I doubt many symbols are going to have multiple dependents, especially when they're being ORed together instead of ANDed. I realize that it makes it easy to clear the map when the base symbol dies, but since every dead symbol sweep hits every symbol anyway that doesn't seem to be a problem. (SymbolDerived works the other way around.)<br></span></blockquote><div><br></div><div>I think you have a good point. Going from base to dependents instead of dependents to base is probably more eager than we need to be. We only need to care if a dependent's lifetime is extended if we think it might be dead. If a dependent looks dead, lazily querying to see if a the base symbol is live seems slightly more efficient to me.</div><div><br></div><div>Anna: what do you think?</div><div><br></div><div>As for not many symbols having multiple dependents, I don't think that's a valid assumption. The whole point of this addition was to give checkers the ability to tie two symbols together (e.g., parameter out value and a return value). There's no reason why there can't be multiple dependents. Even if it's just two checkers that need to track dependencies between a common symbol and another, two is still more than one.</div><div><br></div><blockquote type="cite"><span class="Apple-style-span" style="border-collapse: separate; font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><br>Also, separate from implementation, would it be worth it to use this to /implement/ SymbolDerived? They're basically SymbolRegionValues with dependencies.</span></blockquote></div><br><div>Yes, I had the same thought. That would be a nice cleanup.</div></body></html>