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Talk:Modulinos: Difference between revisions
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Mcandre moved page Talk:Scripted main to Talk:Modulinos: Use community accepted name for this article's content. "Modulinos" is still obscure, but less obscure than my goofy "scripted main" name.
(→What is an "Execuatable library": Defined.) |
m (Mcandre moved page Talk:Scripted main to Talk:Modulinos: Use community accepted name for this article's content. "Modulinos" is still obscure, but less obscure than my goofy "scripted main" name.) |
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:: This current examples are an awful way to use Python's <tt>__name__ == "__main__"</tt> or Ruby's <tt>__FILE__ == $0</tt>. The Python code exports <tt>scriptedmain.main()</tt> and the Ruby code actually defines a global function <tt>main</tt>, which replaces my global function <tt>main</tt> if I defined one before I required the library. I would like to change the Python and Ruby examples to look like <tt>if __name__ == "main": print "It is %s" % meaning_of_life()</tt>, but I am not sure if the task allows me to do this. --[[User:Kernigh|Kernigh]] 22:40, 6 March 2011 (UTC)
::: Kernigh, requires go at the top of files, not after you've declared a main() method. If you deviate from standard programming layouts, you circumvent the language's built-in capabilities, and you're sure to get strange results. --[[User:Mcandre|Mcandre]]
==Name change?==
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:: I think that "library" should be in the page name. I prefer '''"Library with optional main"''', where the optional main is what runs only when I directly run the program, not when I load the library. '''"Library with scripted main"''' would work if we want to keep the "scripted main" phrase. --[[User:Kernigh|Kernigh]] 22:40, 6 March 2011 (UTC)
::: Those aren't bad ideas, and they show that you understand why I created the article. Makes me all warm and fuzzy. --[[User:Mcandre|Mcandre]]
== Some chat in IRC ==
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:I could change the task to reflect what Python does with, for example its CGIHTTPServer module, where calling it as command <code>python -m CGIHTTPServer</code> starts a web server, and loading it as a module would allow the calling program access to code for setting up a web server. --[[User:Paddy3118|Paddy3118]] 16:33, 4 March 2011 (UTC)
C code can use libraries ("shared libraries", "dynamically loaded libraries", whatever...). It's relatively trivial to put all of the logic in a library and have a trivial program that links to that library. That said, this is more about the build process than it is about the C code. (But good practice usually suggests that the "library code" and the "program code" be in separate files.) --[[User:Rdm|Rdm]] 12:16, 7 March 2011 (UTC)
: Can shared libraries be executed ''without'' an extra 'trivial program' though? Python not only has that ability, but it is a documented and well used feature of the language. --[[User:Paddy3118|Paddy3118]] 17:15, 7 March 2011 (UTC)
:: I believe that that is an OS issue. Hypothetically speaking: a shared library that defines a "main()" routine, can be treated as an executable. However if the OS requires something else (like: let's say there is a bit you set: when this bit is set you have an executable, when this bit is cleared you have a shared library), then you need a separate file (so that that bit can be set to different values for each of the two purposes). (With Python, the interpreter itself can serve to make this distinction -- in this case it is the "extra 'trivial program'" (or perhaps not-so-trivial program) that you need to make this work.) --[[User:Rdm|Rdm]] 17:24, 7 March 2011 (UTC)
::: So far it seems there are a lot of examples with no clear definition of what they are about. To require the presence of a compiler for these examples in statically compiled languages is irregular, as most run-time environments for compiled languages do not have the compiler or the source present.
:::The task seems to be a way to get RC as the second place that mentions the page title as well as [http://speely.wordpress.com/2010/11/27/writing-scripts-with-common-lisp/ one blog entry] all from the same person, without enough thought on what ideas are to come under the title.
::: Mcandre needs to answer some more of the points put to him on the purpose of the task - maybe by answering all the questions and suggestions on this talk page).
:::I guess I am against what looks like one persons attempt to popularize their own nebulous idea through RC. Is this a different kind of spam? --[[User:Paddy3118|Paddy3118]] 07:34, 8 March 2011 (UTC)
:::: I don't know. It could simply be a case of [https://thelure.wordpress.com/2010/12/06/tais-model/ Tai's Model], or it ''could be a design pattern without an agreed-upon name.'' I could be wrong, but I think it's likely to be the latter. The name 'scripted main' is in no way clarifying to me as to what the pattern is supposed to do. However, the [https://github.com/mcandre/scriptedmain/blob/45e1ea1521fd541681c6db1468ab0964ed8f9595/README README file] from mcandre's GitHub hosting of his initial examples describes a simple behavior, ''"scriptedmain - Programs that only run main() if they're not loaded as libraries by other programs."'' I really think the better description of this is "write a program which does one thing when executed directly and another thing when loaded as part of a larger program." --[[User:Short Circuit|Michael Mol]] 16:21, 8 March 2011 (UTC)
::::: Yes, there is some confusion over compiled vs scripted vs interpreted vs assembled code and what qualifies as an executable. For the purposes of this article, I consider any ELF/MACH-O/DOS/WIN32 binary file, and any shebang'ed file as an executable. Strictly compiled languages (C, C++, D, Objective C) don't seem to belong in this article, because programs in those languages already have a good idea of what a main() function does and where it belongs. But, in the subset of compiled languages, some people prefer not to use separate files for API and CLI. E.g., "weak" allows this in C/C++.
:::::: I think windows COM servers would be an example of doing this kind of thing with a compiled language. It is, of course, OS specific. But the whole concept of "executable" is also OS specific. Tasks which ask us for a subtle variation on an OS specific concept would typically be OS specific tasks. --[[User:Rdm|Rdm]] 16:19, 12 May 2011 (UTC)
::::: For major scripting languages (Perl, Python, Ruby), it's often assumed that API and CLI work together. To beat a dead horse, Python's if __name__=="__main__" is a much sought-after snippet (2,030,000 results in Google at last count). Coders want to know how to do this. I think they want to do this in other languages as well.
::::: For languages in the middle (Octave, Common Lisp, Chicken Scheme, Clojure), it's plumb difficult to achieve this behavior. Some languages can only partially do "scripted main"; they either require obscure shebangs (Clojure), or worse, require special commands in the shell (LLVM). If I don't add a runtime example for a language, that means that both "python scriptedmain.py" and "./scriptedmain.py" work as expected. IRC users refuse to help me, claiming that their language's REPL is infinitely better than shell. That may be, but I like to provide standard, POSIX, CLI interfaces whenever possible. It took me hours to wrestle working snippets--other coders shouldn't have to.
::::: I want to get back on IRC and chat with you guys. You seem interested, and rightly curious. In the mean time, feel free to twitter me at @mcandre. --[[User:Mcandre|Mcandre]]
:::::: FWIW, there's no problem with OS-specific examples — that's how life is sometimes — though it's best if they're described as such. It does mean that there's an opportunity to describe how to do it on other operating systems/platforms, but that's all cool. (Re language snootiness, hang in there and fight the good fight. The world is open, not closed.) –[[User:Dkf|Donal Fellows]] 09:53, 13 May 2011 (UTC)
== Ambiguities ==
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:That said, my current impression is that you are asking us to illustrate putting the API in a separate file from the definition of "main". If that is the case, many of the examples here (including the one I wrote) are incorrect. --[[User:Rdm|Rdm]] 13:49, 6 March 2011 (UTC)
:: I was wrong about using a blank header file, but one of you on #rosettacode helped me write a definitely working version using the "weak" attribute. Thanks much.
:: My examples could certainly be cleaned up or even patched up. They're currently a work in progress--see the activity at GitHub. https://github.com/mcandre/scriptedmain/commits/master
:: My hope is that once everyone understand the purpose of this article, people will contribute more and more examples until a "scripted main" can be written in almost any language, and those for which scripted main is impossible will be documented so that coders don't waste time trying. --[[User:Mcandre|Mcandre]]
== Is this something like what you want to show? ==
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:Seems close; but the central idea of what the task is about needs work before anyone can judge. I propose we work first on what the task is about; next, on whethere the idea is general enough to be in RC; then on language implementations. --[[User:Paddy3118|Paddy3118]] 07:01, 7 March 2011 (UTC)
:No, your Java example seems wrong to me. The current task description says to ''"to execute a main() function only when a program is run directly"''. So call MainClass.main() only when running MainClass? Your example is wrong because it also calls MainClass.main() when running TestClass? --[[User:Kernigh|Kernigh]] 02:10, 9 March 2011 (UTC)
:Mwn3d, see the current Java example, "ScriptedMain". The comments above about "library as an executable" are on point. The desired behavior is that the ScriptedMain class runs a main method, Test imports ScriptedMain, and Java does not call ScriptedMain.main() when Test is run. --[[User:Mcandre|Mcandre]]
==What ''is'' an "Executable library"==
''(This section needs expansion and discussion to see if we have enough to create a task that is capable of being completed by enough languages.)'' --[[User:Paddy3118|Paddy3118]] 07:45, 7 March 2011 (UTC)
Since my words only carry so far, someone else wrote a short description of this behavior at [http://stackoverflow.com/questions/1973373/why-does-it-do-this-if-name-main/1973391#1973391 Stack Overflow]. --[[User:Mcandre]]
When given a task in a programming 'contest' such as to create a simple function and to find values of that function at certain points; then you would be giving your example in the form of an executable library if:
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--[[User:Paddy3118|Paddy3118]] 07:45, 7 March 2011 (UTC)
: Perfect example Paddy! Is Rosetta Code's main purpose to help coders in programming contests, or are you just framing the article with that mindset for easier reading? --[[User:Mcandre|Mcandre]]
:: Hi Mcandre, I was 'framing' with an eye to maybe rewriting the task goals in a manner that was easier for more people to understand. I'm glad that we are on the same wavelength so far on the goals, but as a task description, the above has holes:
::# It needs to specify a task for the program that is importing the library to do. Maybe: ''"Use the libraries hailstone function, in the standard manner, (or document how this use deviates from standard use of a library); to find the hailstone length returned most often for 1 <= n < 100,000"''
::# It needs a solution in another language
::# It would be good, but probably not essential to get a solution in another non-scripting language too.
:: '''Here is more to flesh out an initial Python solution:'''
::<lang python>from collections import Counter
from executable_hailstone_library import hailstone
def hailstone_length_frequency(hrange):
return Counter(len(hailstone(n)) for n in hrange).most_common()
if __name__ == '__main__':
upto = 100000
hlen, freq = hailstone_length_frequency(range(1, upto))[0]
print("The length of hailstone sequence that is most common for\n"
"hailstone(n) where 1<=n<%i, is %i. It occurs %i times."
% (upto, hlen, freq))</lang>
::'''Sample output''':
::<code>The length of hailstone sequence that is most common for</code>
::<code>hailstone(n) where 1<=n<100000, is 72. It occurs 1467 times</code>
:: '''So, who's for the change!''' --[[User:Paddy3118|Paddy3118]] 08:15, 13 March 2011 (UTC)
::: Good stuff. My only concern with hailstone vs meaning of life is that the hailstone sequence may warrant its own article, the duplication may confuse both hailstone geeks and scripting geeks, and the meaning of life snippet is much simpler to read, write, and understand. One caveat I can think of for the meaning of life example is that it fails to demonstrate export of a useful function ("return 42" is not a useful function). The function must be useful enough that the reader understands why it's worthing coding as both a command line script and as an API, yet useless enough that it's not duplicating another article. If you're set on using the hailstone sequence, feel free to borrow code from [https://github.com/mcandre/cspace My Github] --[[User:Mcandre|Mcandre]]
:::: Hi Mcandre, the new task [[Executable library]] allows people to copy code from the pre-existing [[Hailstone sequence]] task. Check it out. --[[User:Paddy3118|Paddy3118]] 10:25, 4 April 2011 (UTC)
====On fleshing-out a rewrite====
I'll check-back over the next 12 hours and, with enough support of the points I made, move and rewrite the task.
(Thanks for the Ruby support)! --[[User:Paddy3118|Paddy3118]] 05:18, 14 March 2011 (UTC)
=====[[Ruby]]=====
Yes, I guess that it would be a good idea to change all the examples to hailstone libraries. Here is [[Ruby]] code. Might require Ruby 1.9.
<lang ruby># hailstone.rb
module Hailstone
def sequence(n)
seq = [n]
seq << (n = if n.even? then n / 2 else n * 3 + 1 end) until n == 1
seq
end
module_function :sequence
if __FILE__ == $0
big_hs = Enumerator.new do |y|
(1...100_000).each { |n| y << sequence(n) }
end.max_by { |hs| hs.size }
puts "#{big_hs[0]} has a hailstone sequence length of #{big_hs.size}."
puts "The largest number in that sequence is #{big_hs.max}."
end
end</lang>
<lang ruby># hsfreq.rb
require 'hailstone'
module Hailstone
def most_common_length(enum)
h = Hash.new(0)
enum.each { |n| h[sequence(n).length] += 1 }
h.max_by { |length, count| count }
end
module_function :most_common_length
if __FILE__ == $0
last = 99_999
length, count = most_common_length(1..last)
puts "Given the hailstone sequences for 1 to #{last},"
puts "the most common sequence length is #{length},"
puts "with #{count} such sequences."
end
end</lang>
<pre>$ ruby19 hailstone.rb
77031 has a hailstone sequence length of 351.
The largest number in that sequence is 21933016.
$ ruby19 -I. hsfreq.rb
Given the hailstone sequences for 1 to 99999,
the most common sequence length is 72,
with 1467 such sequences.</pre>
--[[User:Kernigh|Kernigh]] 04:16, 14 March 2011 (UTC)
== New goals that could possibly be integrated into this ==
Some languages (like gambas and visual basic) support two startup modes. Applications written on these platforms start with an open window that waits for events, and it is necessary to do some jiggerypokery to cause a main procedure to run instead. I was going to create a new task to demonstrate how to achieve this, and then I remembered this "scripted main". Maybe this can be reorganized to include these requirements? It is not necessarily a "scripted" main, because visual basic is compiled, so we would probably need a rename, though I have not decided on a name for this yet, I am open to ideas. [[User:Markhobley|Markhobley]] 21:58, 11 July 2011 (UTC)
:FWIW in documentation that I have written, this is usually headed "Making the application startup from a main routine". [[User:Markhobley|Markhobley]] 22:08, 11 July 2011 (UTC)
:I would vote to start a new draft task for new topics as this is marked for a slow, lingering, death :-)
:I was wondering however, in your proposed task? Is it about, for example, clicking on a script file in windows to get the script to run versus clicking on the executable to get a [[wp:REPL|REPL]] to run on Windows? --[[User:Paddy3118|Paddy3118]] 06:34, 12 July 2011 (UTC)
::No. The jiggerypokery is done at project build time, not at run time invocation, so that would be a separate task. [[User:Markhobley|Markhobley]] 07:30, 12 July 2011 (UTC)
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