I was guessing that the current proposal does not change anything re. default and current member wise initializers and so in addition to suggesting Scala syntax I was also suggesting the transformation shown, or its equivalent. The advantage of having a member wise init that has default arguments and argument labels are considerable:<div><br></div><div>1. Allows lets as well as vars </div><div>2. Allows partial custom initialization </div><div>3. Eliminates need for other mechanisms, i.e. default and existing member wise initialization </div><div><br></div><div>These facilities could be added to `memberwise init(...)` as well. In particular, if a member wise init was present then an initialized property could have a label, e.g.:</div><div><br></div><div> class C {</div><div> let example name: Type = initial</div><div> memberwise init(...)</div><div> }</div><div><br></div><div>Would become the equivalent of:</div><div><br></div><div> <font size="2"><span style="background-color:rgba(255,255,255,0)"> class C {</span></font></div><div><font size="2"><span style="background-color:rgba(255,255,255,0)"> let name: Type</span></font></div><div><font size="2"><span style="background-color:rgba(255,255,255,0)"> init(</span></font><span style="background-color:rgba(255,255,255,0);font-size:small">example name: Type = initial) {</span></div><div><span style="background-color:rgba(255,255,255,0);font-size:small"> <a href="http://self.name">self.name</a> = name</span></div><div><span style="background-color:rgba(255,255,255,0);font-size:small"> }</span></div><div><font size="2"><span style="background-color:rgba(255,255,255,0)"> }</span></font></div><div><br></div><div>The Scala syntax is just a shorter alternative, ideally there be a discussion of the pros and cons of the two syntax that included the possibility of the wider set of objectives as outlined in the numbered points above.</div><div><br>On Tuesday, 5 January 2016, Matthew Johnson <<a href="mailto:matthew@anandabits.com">matthew@anandabits.com</a>> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word"><br><div><blockquote type="cite"><div>On Jan 4, 2016, at 5:48 PM, Howard Lovatt <<a href="javascript:_e(%7B%7D,'cvml','howard.lovatt@gmail.com');" target="_blank">howard.lovatt@gmail.com</a>> wrote:</div><br><div><div style="word-wrap:break-word">Yes you can get close, but:<div><br></div><div>1. Its weird that you can only do this in an extension.</div></div></div></blockquote><div><br></div><div>This is the way the current implicit initializer works. It is not synthesized if you define any initializers in the body of the type. There are good reasons it works this way and the current proposal does not change those rules.</div><br><blockquote type="cite"><div><div style="word-wrap:break-word"><div>2. Its not quite the same as the proposal the current member-wise initialiser does not make the init arguments optional (the arguments themselves do not have defaults), i.e. with your example `let defaultOriginRect = Rect(size: Size(width: 5.0, height: 5.0))` fails whereas it would work for the proposal (this could also be true if the existing struct memberwise init and the new `memberwise init(..)` where changed to provide init argument defaults).</div></div></div></blockquote><div><br></div><div>The implicit memberwise initializer currently in the language does not provide defaults for parameters. This proposal changes that behavior and provides defaults if the the member is a `var` and has an initial value. </div><div><br></div><div>Unfortunately I was not able to find a solution to allow synthesized parameters for `let` members to have default values. This is because the current semantics for `let` members do not allow the member to be initialized to anything other than the initial value if one is provided. I am hoping a solution to this will be identified in the future and have suggested one possible mechanism `@default` in the future enhancements section.</div><br><blockquote type="cite"><div><div style="word-wrap:break-word"><div>3. Only ‘really' works for structs, the compiler doesn’t write a member-wise initialiser for classes (just a default initializer).</div></div></div></blockquote><div><br></div><div>That is true about the current behavior of the language but is not true with regards to the current proposal.</div><br><blockquote type="cite"><div><div style="word-wrap:break-word"><div>4. Still need the compiler to provide both default and member-wise initialisers, whereas this proposal would allow the existing default and member-wise initialisers to be deprecated and just the new member-wise initialiser would remain which would simplify the language and make it clear what was happening (this could also be true if a `memberwise init(..)` where added and existing compiler written inits removed).<br></div></div></div></blockquote><div><br></div><div>This proposal does not change anything with regard to the default initializer.</div><br><blockquote type="cite"><div><div style="word-wrap:break-word"><div><div><br>
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<br><div><blockquote type="cite"><div>On 5 Jan 2016, at 10:16 AM, Matthew Johnson <<a href="javascript:_e(%7B%7D,'cvml','matthew@anandabits.com');" target="_blank">matthew@anandabits.com</a>> wrote:</div><br><div><div style="font-family:Helvetica;font-size:12px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">struct Rect { var origin: Point = Point(), size: Size = Size() }</div><div style="font-family:Helvetica;font-size:12px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">extension Rect {</div><div style="font-family:Helvetica;font-size:12px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"> init(center: Point, size: Size) {<br><blockquote type="cite"></blockquote> let originX = center.x - (size.width / 2)<br><blockquote type="cite"></blockquote> let originY = center.y - (size.height / 2)<br><blockquote type="cite"></blockquote> self.init(origin: Point(x: originX, y: originY), size: size)<br><blockquote type="cite"></blockquote> }</div><div style="font-family:Helvetica;font-size:12px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">}</div></div></blockquote></div><br></div></div></div></blockquote></div><br></div></blockquote></div><br><br>-- <br> -- Howard.<br><br>