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<p class="MsoNormal">Hola ;)</p>
<p class="MsoNormal">Interesting... a few quick observations:</p>
<p class="MsoNormal">1) from the Smalltalk point of view anything between two square brackets is a block and would not evaluate until sent #value; however this</p>
<p class="MsoNormal">[succ: n | n + 1]</p>
<p class="MsoNormal">would be a syntactic sugar for </p>
<p class="MsoNormal">succ := [:n | n + 1] </p>
<p class="MsoNormal">which means there would be "some" evaluation (assignment) even without sending #value (because it's a syntactic sugar). Just saying it may be a bit confusing or inconsistent…</p>
<p class="MsoNormal">2) I understand Smalltalk is (or at least used to be) an LL(1) language; correct me if I'm wrong but your suggestion would make the grammar LL(2) or more because '[' followed by an identifier still doesn’t distinguish between possible branches
and you have to look further ahead…</p>
<p class="MsoNormal">3) how would you parse [ x | y ] ... as a block with an "or" clause or an extension notation for x := [ y ] ?</p>
<p class="MsoNormal">Best,</p>
<p class="MsoNormal">Jaromir</p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNoSpacing"><span lang="CS">--</span></p>
<p class="MsoNoSpacing"><strong><span style="font-family:"Calibri Light",sans-serif;color:#333333;font-weight:normal">Jaromír Matas</span></strong><span style="font-family:"Calibri Light",sans-serif;color:#555555"><o:p></o:p></span></p>
<p class="MsoNoSpacing"><span style="font-family:"Calibri Light",sans-serif;color:#2E75B6">mail@jaromir.net</span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal" style="border:none;padding:0in"><b>From: </b><a href="mailto:cuis-dev@lists.cuis.st">Francisco Garau via Cuis-dev</a><br>
<b>Sent: </b>Friday, July 15, 2022 20:39<br>
<b>To: </b><a href="mailto:cuis-dev@lists.cuis.st">cuis-dev@lists.cuis.st</a><br>
<b>Cc: </b><a href="mailto:francisco.garau@gmail.com">Francisco Garau</a><br>
<b>Subject: </b>[Cuis-dev] extending the syntax for blocks and methods</p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Hola Amigos -- just wanted to share with you some ideas I've been thinking about for a while. <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">It all started when someone mentioned the colon in the syntax for block arguments could have whitespace around the argument so that you could write
<span style="font-family:"Courier New"">[ : n | n + 1] </span><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">It makes perfect sense to see the block as an "inlined" method that doesn't require any method-lookup; therefore, the selector is superfluous. But if we accepted the selector inside the block, it could be used as the variable holding the
block. So, instead of writing <span style="font-family:"Courier New"">succ := [:n | n + 1]</span> we could write
<span style="font-family:"Courier New"">[succ: n | n + 1]</span> <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Even better if the block evaluation accepts #: as a valid selector. So you could write
<span style="font-family:"Courier New"">(succ: 3) = 4</span> instead of <span style="font-family:"Courier New"">(succ value: 3) = 4</span>. <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">A short example will make this clear. <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Vanilla Smalltalk<o:p></o:p></p>
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<p class="MsoNormal">succ := [:n | n + 1].<o:p></o:p></p>
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<p class="MsoNormal">(succ value: 3) = 4. <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Extended Block Syntax<o:p></o:p></p>
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<p class="MsoNormal">[succ: n | n + 1]. <o:p></o:p></p>
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<p class="MsoNormal">(succ: 3 ) = 4. <o:p></o:p></p>
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<p class="MsoNormal">"the above is equivalent to" <o:p></o:p></p>
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<p class="MsoNormal">(succ perform: #: with: 3) = 4. <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Being able to parse blocks with these syntax paves the way to unify the syntax for method definition—for example, a few hypothetical methods from the Point class. <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">"Point class>x:y:" <o:p></o:p></p>
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<p class="MsoNormal">[x: xInteger y: yInteger | <o:p></o:p></p>
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<p class="MsoNormal"> ^self basicNew setX: xInteger setY: yInteger].<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">"Point>>abs"<o:p></o:p></p>
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<p class="MsoNormal">[abs | <o:p></o:p></p>
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<p class="MsoNormal"> ^x abs @ y abs]. <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">"Point>>extent:" <o:p></o:p></p>
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<p class="MsoNormal">[extent: aPoint |<o:p></o:p></p>
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<p class="MsoNormal"> ^Rectangle origin: self extent: aPoint] <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Of course, it gets trickier when blocks have more than one argument.. <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">[add: a to: b | a + b]. <o:p></o:p></p>
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<p class="MsoNormal">(add_to value: 3 value: 4) = 7. "old style block evaluation" <o:p></o:p></p>
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<p class="MsoNormal">(add: 3 to: 4) = 7. <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">I think building a separate Parser is a sensible approach -- is there a Smalltalk Parser as a separate package that can be tweaked without affecting the running image?<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Thanks,<o:p></o:p></p>
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<p class="MsoNormal">Francisco<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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