Challenge: A Self-Replicating App

William Lancee

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@aeric Thank you for the link. That was my sentiment exactly. My early experience with this phenomenon was in 1971. Also I love Hofstadter's book, I am looking at now on my shelf.

I just finished reading the material in the link. Fascinating!
 
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sorex

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aeric said:
I handled the double quote in inelegant way by using Replace.
Click to expand...

you could save a line if you used the QUOTE constant

in case the readers didn't notice yet my routine even uses some sort of iteration to make it work
in the long line the same call is used again to feed data.
 

aeric

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William Lancee said:
@aeric Thank you for the link. That was my sentiment exactly. My early experience with this phenomenon was in 1971. Also I love Hofstadter's book, I am looking at now on my shelf.

I just finished reading the material in the link. Fascinating!
Click to expand...
I didn't read all the page. I just refer to the sample given and get the idea. Thanks for introducing this concept as a quiz. I found it interesting and just tried out.
 

aeric

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sorex said:
you could save a line if you used the QUOTE constant

in case the readers didn't notice yet my routine even uses some sort of iteration to make it work
in the long line the same call is used again to feed data.
Click to expand...
Ya, I believe my code can be improved further. It was 1am when I feel boring with my project and I saw this thread. I almost gave up when I can't figure out the quotation marks. I run my code, copy the Textarea content into another test window, and B4J immediately highlight the read lines. That time around 5am i just decided to use some tricks to make it works (at least once).

In fact, if you copy the textarea content again from the second compile, it is not working! ?
 
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sorex

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yeah, that's the hard part of it. you need to do the run>copy>paste>run 2 or 3 times to be sure it's working right.
 

William Lancee

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Thank you @udg @sorex @aeric for participating. I certainly enjoyed seeing how you did it. I also learned from the link @aeric posted

https://en.wikipedia.org/wiki/Quine_(computing)

that this is a well-known puzzle, solved in most programming languages - now it is solved in B4X!

If you read the Wiki article, you'll find a Java program that outputs a C++ program that outputs the original Java program.

This feat has an official name: "ouroboros programs" or "quine-relays".
 
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sorex

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I had a look at the page and see some simularities in William's & @aeric 's code. Both of you use this kind of chunck copying loops like in the article.
 

William Lancee

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This my last word on this topic. I thought that if anyone looks at this thread in the future, they may be interested in a streamlined version that is able to replicate on B4A and B4J and then it will run on either platform. It is also transparent enough to be understood by all.

B4X: 
Sub Process_Globals
    Private sb(3) As StringBuilder
    Private startName As String = "Activity_Create(FirstTime As Boolean)"
End Sub
#if B4J
Sub AppStart (Form1 As Form, Args() As String)
    startName = "AppStart (Form1 As Form, Args() As String)"
#else if B4A
Sub Globals
End Sub
Sub Activity_Create(FirstTime As Boolean)
#end if
    sb(0).initialize: sb(1).initialize: sb(2).initialize
    toLines(0, "Sub Process_Globals")
    toLines(0, "    Private sb(3) As StringBuilder")
    toLines(0, "    Private startName As String = 'Activity_Create(FirstTime As Boolean)'")
    toLines(0, "End Sub")
    toLines(0, "#if B4J")
    toLines(0, "Sub AppStart (Form1 As Form, Args() As String)")
    toLines(0, "    startName = 'AppStart (Form1 As Form, Args() As String)'")
    toLines(0, "#else if B4A")
    toLines(0, "Sub Globals")
    toLines(0, "End Sub")
    toLines(0, "Sub Activity_Create(FirstTime As Boolean)")
    toLines(0, "#end if")
    toLines(0, "    sb(0).initialize: sb(1).initialize: sb(2).initialize")
    toLines(2, "    Log(sb(0).Append(sb(1).ToString).Append(sb(2).toString).toString)")
    toLines(2, "End Sub")
    toLines(2, "Sub toLines(i As Int, s As String)")
    toLines(2, "    If i = 0 Then s = s.Replace('*', startName)")
    toLines(2, "    sb(i).Append(s.Replace(Chr(39), QUOTE) & CRLF)")
    toLines(2, "    sb(1).Append(TAB & 'toLines(' & i & ', ' & QUOTE & s & QUOTE & ')' & CRLF)")
    toLines(2, "End Sub")
    Log(sb(0).Append(sb(1).ToString).Append(sb(2).toString).toString)
End Sub
Sub toLines(i As Int, s As String)
    If i = 0 Then s = s.Replace("*", startName)
    sb(i).Append(s.Replace(Chr(39), QUOTE) & CRLF)
    sb(1).Append(TAB & "toLines(" & i & ", " & QUOTE & s & QUOTE & ")" & CRLF)
End Sub
 
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