John, the question was specifically about the quotation parameter's stack effects in general, i.e. `quot: ( x -- x )` vs. simply `quot` in the parameter lists.
My take is that the quotation stack effects are not checked separately on a per-parameter basis, only the word as a whole is checked. So, they are merely for documentation purposes, and may be incorrect with no penalty. From the documentation: "For words that are not inline, only the number of inputs and outputs carries semantic meaning, and effect variables are ignored."
http://docs.factorcode.org/content/article-effects.html
01.06.2017, 05:33, "John Benediktsson" <mrj...@gmail.com>:
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:Factor-talk@lists.sourceforge.net><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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