<HTML><BODY style="word-wrap: break-word; -khtml-nbsp-mode: space; -khtml-line-break: after-white-space; "><BR><DIV><DIV>On Aug 27, 2007, at 1:29 AM, Igor Stasenko wrote:</DIV><BR class="Apple-interchange-newline"><BLOCKQUOTE type="cite"><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Cascade is useful. It allows me to write code like that:</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><SPAN class="Apple-tab-span" style="white-space:pre"> </SPAN><SPAN class="Apple-tab-span" style="white-space:pre"> </SPAN>ogl</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><SPAN class="Apple-converted-space"> </SPAN>glTexParameteri: GLTexture2d with: GLTextureMinFilter</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">with: GLLinear;</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><SPAN class="Apple-tab-span" style="white-space:pre"> </SPAN><SPAN class="Apple-tab-span" style="white-space:pre"> </SPAN>glTexParameteri: GLTexture2d with: GLTextureMagFilter with: GLLinear;</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><SPAN class="Apple-tab-span" style="white-space:pre"> </SPAN><SPAN class="Apple-tab-span" style="white-space:pre"> </SPAN>glTexParameteri: GLTexture2d with: GLTextureWrapS with: GLClamp;</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><SPAN class="Apple-tab-span" style="white-space:pre"> </SPAN><SPAN class="Apple-tab-span" style="white-space:pre"> </SPAN>glTexParameteri: GLTexture2d with: GLTextureWrapT with: GLClamp;</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><SPAN class="Apple-tab-span" style="white-space:pre"> </SPAN><SPAN class="Apple-tab-span" style="white-space:pre"> </SPAN>glPixelMapfv: GLPixelMapIToA with: 2 with: (FloatArray with: 0.0 with: 1.0).</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; min-height: 14px; "><BR></DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">But at the same time it stinks because you don't using the evaluation</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">result of previously sent message, you simply drop it. And from this</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">point i feel that something wrong with such design. Why computer needs</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">to waste cycles to evaluate result of message when its simply not used</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">at the end?</DIV></BLOCKQUOTE><DIV><BR class="khtml-block-placeholder"></DIV><DIV>For side effects ! :-)</DIV><BR><BLOCKQUOTE type="cite"><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; min-height: 14px; "></DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">In contrast , a pipe does not drops evaluation result, but reuses it</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">in expression that follows. From this point i like it more than</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">cascade.</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; min-height: 14px; "><BR></DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Same with period '.'</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Each time you placing a period in code, you telling compiler to drop</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">the evaluated result of your expression.</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Can it be considered as good from computational point of view? Of</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">course its not. You forcing a computer to waste the cycles just for</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">nothing.</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; min-height: 14px; "><BR></DIV></BLOCKQUOTE><DIV><BR class="khtml-block-placeholder"></DIV>Same here for side effects.</DIV><DIV><BR><BLOCKQUOTE type="cite"><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; min-height: 14px; "></DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Same with implicit return self from a method. I see a good reasons why</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">i don't want return anything from a method, because it returns nothing</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">useful or meaningful, and never used for continue evaluation in other</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">expressions.</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; min-height: 14px; "><BR></DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">And i think that maybe from computational<SPAN class="Apple-converted-space"> </SPAN>point of view, it might be</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">useful to indicate if we need to return result from a method or don't.</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">So, all messages which chained in cascade expressions can be sent with</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">flag 'drop result=true' and same for messages which is the last before</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">period '.'. In other words we can have two forms of 'send' operation</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">(bytecode): Send with return and send without return.</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">I think this can save us from wasting a processor cycles just for nothing.</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">I know that such semantics belongs mainly to compiler, not language</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">itself, but i just want to point out, how language design influences</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">the implementation, and how good or bad it can turn out at the end.</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; min-height: 14px; "><BR></DIV> </BLOCKQUOTE></DIV><BR><DIV><SPAN class="Apple-style-span" style="border-collapse: separate; border-spacing: 0px 0px; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; text-align: auto; -khtml-text-decorations-in-effect: none; text-indent: 0px; -apple-text-size-adjust: auto; text-transform: none; orphans: 2; white-space: normal; widows: 2; word-spacing: 0px; "><DIV>This is a very old question on purity and side-effect that seems to have reached a certain kind of agreement with Monads.</DIV><DIV>Lots of papers treat this issue. Some suggested Effects Typing, some Continuations, then the Haskell guys figured</DIV><DIV>out that with type classes they could create a polymorphic monadic bind and did the trick.</DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV>But I think that what you say doesn't apply to Smalltalk because it's dynamically typed.</DIV><DIV>How would you know at compile time if a method does side-effects ....</DIV><DIV>What if a method called in a cascade does side effects , but the cascade itself seems pure ?</DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV>I think it's complex stuff...</DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV>Haskell does the "markings" (excuse the name) you talk about with monads </DIV><DIV>and anything "not marked" doesn't do any sideffects, it's pure.</DIV><DIV>By adding graph manipulation (reducing & updating) at runtime they evaluate functions "by name"</DIV><DIV>and than by updating the runtime graph they avoid re-computation.</DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV>In haskell basically every expression is in a [ ... ] (well sort of they use graph manipulation)</DIV><DIV>And it's sent the message value only if needed. And when the the value it's returned the block gets </DIV><DIV>removed and it's updated with the value... so no more need to evaluate it, if you need it again.</DIV><DIV>It's a powerful optimization ! Too bad that to get that you need to but Everything in a [ ... ] </DIV><DIV>(strictness analysis fixes that a bit).</DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV>But the price to pay is high in my opinion ... </DIV><DIV>functional becomes beautiful, but imperative stuff is a bit too hard ( not syntactically because of the 1 ton of syntax sugar) </DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV> </DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV> </DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV><BR class="khtml-block-placeholder"></DIV><BR class="Apple-interchange-newline"></SPAN> </DIV><BR></BODY></HTML>