Well, technically neither ``dip`` nor ``keep`` need those stack effects,
they are inlined which means the non-inline word that includes them will
have it's stack effect checked by the compiler for correctness.
There are few reasons why we want to have the ".." variadic stack effects,
and those are useful in the stack-checker and visually for documentation,
but if you removed them and tried to compile a word that was incorrect, it
would give you a worse error message but still give you an error.
On Wed, May 31, 2017 at 7:03 PM, Sankaranarayanan Viswanathan <
rationalrev...@gmail.com> wrote:
> Thanks for the ideas John!
>
> I have been looking at the collection of talks, and they've been quite
> helpful. Your thoughts about discussing "Java like" things makes a lot of
> sense and I think contrasting Factor's object system with Java's should be
> a nice topic.
>
> That said, I did run into a question preparing the slides related to
> stack-effects. I noticed that some combinators do not specify stack effects
> for quotation inputs.
>
> e.g.
> dip ( x quot -- x )
> keep ( ..a x quot: ( ..a x -- ..b ) -- ..b x )
>
> Why does `dip` not need to specify the quotations stack effect, but `keep`
> did? I suspect they also have something to do with the inline word, but I'm
> not really sure. Could you explain?
>
> Thanks,
> Sankar
>
>
>
> On 5/30/17 11:47 PM, John Benediktsson wrote:
>
>> We have a few "talks" that were given a number of years ago (not all
>> code in them is up to date, but it's mostly good -- if you have problems
>> updating the code let me know and I can help):
>>
>> https://github.com/factor/factor/tree/master/extra/talks
>>
>> https://github.com/slavapestov/boston-lisp-talk
>>
>> https://github.com/slavapestov/emerging-langs-talk
>>
>> You might find it interesting to discuss "Java-like" things, for
>> example, interfaces vs protocols:
>>
>> public interface Foo {
>> String a();
>> int b();
>> }
>>
>> public class FooImpl {
>> public String a() { return "hello" } ;
>> public int b() { return 42 } ;
>> }
>>
>> vs a protocol (two generic methods) and a concrete class that implements
>> it...
>>
>> GENERIC: a ( obj -- a )
>> GENERIC: b ( obj -- a )
>>
>> TUPLE: foo ;
>> M: foo a "hello" ;
>> M: foo b 42 ;
>>
>> Could also talk about ``SINGLETON:``, so instead of (plus or minus
>> thread safety):
>>
>> public class Foo {
>> private static _instance = null;
>> public static Foo getInstance() {
>> if ( _instance == null ) { _instance = new Foo() };
>> return _instance;
>> }
>> }
>>
>> vs.
>>
>> SINGLETON: foo
>>
>> So, touching on code generation and higher level concepts.
>>
>> Maybe macros might be interesting?
>>
>> Some other ideas from my blog, not sure of your audience's interest:
>>
>> https://re-factor.blogspot.com/2009/08/calculating-with-ebnf.html
>>
>> https://re-factor.blogspot.com/2010/11/estimating-cpu-speed.html
>>
>> https://re-factor.blogspot.com/2011/02/simple-rpg.html
>>
>> https://re-factor.blogspot.com/2011/04/powers-of-2.html
>>
>> https://re-factor.blogspot.com/2011/04/mail-with-gui.html
>>
>> https://re-factor.blogspot.com/2011/07/concatenative-thinking.html
>>
>> https://re-factor.blogspot.com/2011/07/one-liners.html
>>
>> https://re-factor.blogspot.com/2011/08/printf.html
>>
>> https://re-factor.blogspot.com/2012/02/readability.html
>>
>> https://re-factor.blogspot.com/2012/08/literate-programming.html
>>
>> https://re-factor.blogspot.com/2013/10/rock-paper-scissors.html
>>
>> https://re-factor.blogspot.com/2015/06/send-more-money.html
>>
>> https://re-factor.blogspot.com/2017/02/711.html
>>
>> Best,
>> John.
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> On Tue, May 30, 2017 at 8:14 PM, Sankaranarayanan Viswanathan
>> <rationalrev...@gmail.com
>> <mailto:rationalrev...@gmail.com>> wrote:
>>
>> Hi Guys,
>>
>> We have a developer community at where I work, and we do monthly
>> tech talks that usually last between 30 and 40 minutes. I presume
>> very few in that group have looked at stack based languages before,
>> and I've been wanting to do a small talk about Factor there.
>>
>> After spending a week preparing slides, I'm having a bit of trouble
>> understanding what would be a meaningful scope for my talk. I really
>> want to touch upon a couple of aspects:
>> - show what stack based code looks like (i.e. avoid naming
>> variables most of the time)
>> - show that all syntax is just words, and that syntax is extensible
>> - show a little of the help system
>> - show a bit of the interactive development workflow (change,
>> refresh, test)
>>
>> But, I'm suspecting before I even get here I might need to spend a
>> lot of time talking about stack-effects, combinators, and other
>> basics before they might get a feel for what factor code feels like.
>> And this I'm afraid might be a little too much to digest in a short
>> time. Words like dip, bi@ and sequence combinators like map seem
>> fundamental to work with factor, and I'm afraid a short presentation
>> might not be the best place to introduce these topics. But, without
>> them code examples are going to be hard to understand.
>>
>> Any ideas?
>>
>> Thanks,
>> Sankar
>>
>>
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>
>
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