Merge pull request #3851 from Abigail/abigail/week-107

Abigail/week 107

45 files changed, 643 insertions, 77 deletions

diff --git a/challenge-107/abigail/README.md b/challenge-107/abigail/README.md
index 3b4bc6fcf4..67392c9e54 100644
--- a/challenge-107/abigail/README.md
+++ b/challenge-107/abigail/README.md
@@ -1,108 +1,157 @@
 # Solution by Abigail
-## [Maximum Gap](https://perlweeklychallenge.org/blog/perl-weekly-challenge-106/#TASK1)
+## [Self-descriptive Numbers](https://perlweeklychallenge.org/blog/perl-weekly-challenge-107/#TASK1)
 
-You are given an array of integers `@N`.
+Write a script to display the first three self-descriptive numbers.
+As per [wikipedia](https://en.wikipedia.org/wiki/Self-descriptive_number),
+the definition of Self-descriptive Number is
 
-Write a script to display the maximum difference between two
-successive elements once the array is sorted.
+> In mathematics, a self-descriptive number is an integer `m` that in a
+> given base `b` is `b` digits long in which each digit `d` at position `n`
+> (the most significant digit being at position 0 and the least
+> significant at position `b - 1`) counts how many instances of
+> digit `n` are in `m`.
 
-If the array contains only `1` element then display `0`.
-
-### Examples
+### Example
 ~~~~
-Input: @N = (2, 9, 3, 5)
-Output: 4
+ 1210 is a four-digit self-descriptive number:
 
-Input: @N = (1, 3, 8, 2, 0)
-Output: 5
+    position 0 has value 1 i.e. there is only one 0 in the number
+    position 1 has value 2 i.e. there are two 1 in the number
+    position 2 has value 1 i.e. there is only one 2 in the number
+    position 3 has value 0 i.e. there is no 3 in the number
+~~~~
 
-Input: @N = (5)
-Output: 0
+### Output
 ~~~~
+    1210, 2020, 21200
+~~~~
+
+### Notes
+
+This is a trivial exercise -- as all exercises are which do not
+take any input, and which have a fixed output. Fixed output
+challenges are boring -- unless there's another condition (golf,
+for instance).
+
+This exercise is so trivial, we don't even have to head to the OEIS
+to download the wanted numbers, as the expected output is stated
+in the exercise.
+
+So, all we need to do is print three numbers, separated by commas.
+
+The easiest way would be to just do what the challenge demands
+from us, and print the output as given.
+
+A slightly less easy way would be to head over the given
+[Wikipedia page](https://en.wikipedia.org/wiki/Self-descriptive_number)
+(or the [OEIS](https://oeis.org) for that matter), copy the first
+three numbers, and print those out.
+
+But those solutions no doubt will cause scorn in two weeks,
+when the review comes out. It's all "advice about the code is the thing".
+
+But that raises the question, what is the code which is wanted? 
+You could generate all the numbers of length `b` in base `b`, while
+increasing `b`, test them for being self-descriptive, and print 
+the first three numbers found.
+
+My advice about brute force code when there is a more efficient way:
+Don't ever do that.
+
+If we just imagine the Wikipedia page didn't list any self-descriptive
+numbers, and Neil Sloane has forgotten to pay the fee for the OEIS
+domain, so it was taken off-line, then it's still easy to determine
+the first three self-descriptive numbers -- no code required.
+
+Given the following observations for a self-descriptive number `N` in base `b`:
+* `N` has `b` digits, and does not start with a `0`.
+* The sum of the digits of `N` is `b`.
+* No digit of `N` equals `b - 1`.
+* The last digit of `N` is `0`.
+* If `b > 4`, then `N` does not start with a `1`.
+* If `b > 4`, then `N` does not start with `b - 2`.
+
+From that, it's easy to determine that:
+* There are no self-descriptive numbers in any base below `4`.
+* A self-descriptive number in base `4` must start with a `1` or `2`. And
+  end with a `0`. If it starts with a `1`, the middle digits are `1` and `2`.
+  If it starts with a `2`, the middle digits are `0` and `2`. Both `1210`,
+  and `2020"`are self-descriptive numbers.
+* A self-descriptive number in base `5` must start with a `2`, and end
+  with a `0`. The three middle digits must be `0`, `1`, and `2`. `21200`
+  is a self-descriptive number.
+
+(For a more detailed derivation, with all the details filled in, see [the blog
+post](https://abigail.github.io/HTML/Perl-Weekly-Challenge/week-107-1.html))
+
+But this still makes this challenge a glorified `Hello, World!`
+program, as there is no useful code to write to generate the numbers.
 
 ### Solutions
-* [GNU AWK](awk/ch-1.gawk)
-* [Bash](perl/ch-1.sh)
+* [AWK](awk/ch-1.awk)
+* [Bash](bash/ch-1.awk)
+* [BASIC](basic/ch-1.bas)
+* [bc](bc/ch-1.bc)
+* [Befunge-93](befunge-93/ch-1.bf93)
 * [C](c/ch-1.c)
+* [Cobol](cobol/ch-1.cb)
+* [Csh](csh/ch-1.csh)
+* [Erlang](erlang/ch-1.erl)
+* [Forth](forth/ch-1.fs)
+* [Fortran](fortran/ch-1.fs)
+* [Go](go/ch-1.go)
+* [Java](java/ch-1.java)
 * [Lua](lua/ch-1.lua)
-* [Node.js](node/ch-1.js)
+* [m4](m4/ch-1.m4)
+* [Node.js](lua/ch-1.js)
+* [OCaml](ocaml/ch-1.ml)
+* [Pascal](pascal/ch-1.pl)
 * [Perl](perl/ch-1.pl)
+* [PHP](php/ch-1.pl)
+* [PostScript](postscript/ch-1.ps)
 * [Python](python/ch-1.py)
+* [R](r/ch-1.r)
+* [Rexx](rexx/ch-1.rexx)
 * [Ruby](ruby/ch-1.rb)
+* [Scheme](scheme/ch-1.scm)
+* [sed](sed/ch-1.sed)
+* [SQL](sql/ch-1.sql)
+* [Tcl](tcl/ch-1.tcl)
 
 ### Blog
-[Perl Weekly Challenge 106: Maximum Gap](https://abigail.github.io/HTML/Perl-Weekly-Challenge/week-106-1.html)
+[Perl Weekly Challenge 107: Self-descriptive Numbers](https://abigail.github.io/HTML/Perl-Weekly-Challenge/week-107-1.html)
 
-## [Decimal String](https://perlweeklychallenge.org/blog/perl-weekly-challenge-106/#TASK2)
+## [List Methods](https://perlweeklychallenge.org/blog/perl-weekly-challenge-107/#TASK2)
 
-You are given numerator and denominator i.e. `$N` and `$D`.
+Write a script to list methods of a package/class.
 
-Write a script to convert the fraction into decimal string. If the
-fractional part is recurring then put it in parenthesis.
-
-### Examples
+### Example
+Given the package:
 ~~~~
-Input: $N = 1, $D = 3
-Output: "0.(3)"
+package Calc;
 
-Input: $N = 1, $D = 2
-Output: "0.5"
+use strict;
+use warnings;
 
-Input: $N = 5, $D = 66
-Output: "0.0(75)"
-~~~~
-
-### Notes
-
-We are assuming the numerator is non-negative, and the denominator
-is positive. Dealing with signs is left as an exercise to the reader.
-
-We're creation the decimal expansion of the fraction `$N / $D`
-by performing long division.
-
-First, we calculate the part before the decimal point, by
-doing integer division of `$N / $D`.
-We're then left to do division of `$N' / $D`, where `$N'` initially
-is `$N % $D`.
-We then repeatedly find new digits by calculating the integer
-division of `(10 * $N' / $D)` (which gives us a new digit in the
-decimal expansion), and then setting `$N' = 10 * $N' % $D`.
-The fraction will have a finite decimal expansion if during the
-process `$N'` becomes `0`. Otherwise, it repeats, and it repeats
-as soon as have a `$N'` which we've already seen. By the pidgeon
-hole principle, this cannot take more then $D steps.
-To calculate the repeating part, we keep track of how far we
-were in calculating the expansion for which `$N'`.
+sub new { bless {}, shift; }
+sub add { }
+sub mul { }
+sub div { }
 
+1;
 ~~~~
-     22/7     \0.318
-        0                      int (7 / 22) == 0, so 0 before decimal point
-        --
-        7                      N =       N  % D
-        66                     3 * D
-        --
-         4                     N = (10 * N) % D   <--+
-         22                    1 * D                 |
-         --                                          |  Same, so '18'
-         18                    N = (10 * N) % D      |  is the repeating
-         176                   8 * D                 |  part
-         ---                                         |
-           4                   N = (10 * N) % D   <--+
+Output:
+~~~~
+BEGIN
+mul
+div
+new
+add
 ~~~~
-
-This implementation is based on the [one given on
-Wikipedia](https://en.wikipedia.org/wiki/Repeating_decimal).
-
 
 ### Solutions
-* [AWK](perl/ch-2.awk)
-* [Bash](bash/ch-2.sh)
-* [C](c/ch-2.c)
-* [Lua](lua/ch-2.lua)
-* [Node.js](node/ch-2.js)
 * [Perl](perl/ch-2.pl)
-* [Python](python/ch-2.py)
-* [Ruby](ruby/ch-2.rb)
 
 ### Blog
-[Perl Weekly Challenge 106: Decimal String](https://abigail.github.io/HTML/Perl-Weekly-Challenge/week-106-2.html)
+[Perl Weekly Challenge 107: List Methods](https://abigail.github.io/HTML/Perl-Weekly-Challenge/week-107-2.html)
+
diff --git a/challenge-107/abigail/awk/ch-1.awk b/challenge-107/abigail/awk/ch-1.awk
new file mode 100644
index 0000000000..cd8a87a7dc
--- /dev/null
+++ b/challenge-107/abigail/awk/ch-1.awk
@@ -0,0 +1,13 @@
+#!/usr/bin/awk
+
+#
+# See ../README.md
+#
+
+#
+# Run as: awk -f ch-1.awk
+#
+
+BEGIN {
+    print "1210, 2020, 21200"
+}
diff --git a/challenge-107/abigail/bash/ch-1.sh b/challenge-107/abigail/bash/ch-1.sh
new file mode 100644
index 0000000000..133a606068
--- /dev/null
+++ b/challenge-107/abigail/bash/ch-1.sh
@@ -0,0 +1,11 @@
+#!/bin/sh
+
+#
+# See ../README.md
+#
+
+#
+# Run as: bash ch-1.sh < input-file
+#
+
+echo "1210, 2020, 21200"
diff --git a/challenge-107/abigail/basic/ch-1.bas b/challenge-107/abigail/basic/ch-1.bas
new file mode 100644
index 0000000000..6f0a11aabb
--- /dev/null
+++ b/challenge-107/abigail/basic/ch-1.bas
@@ -0,0 +1,9 @@
+010 REM 
+020 REM See ../README.md
+030 REM 
+
+040 REM 
+050 REM Run as: basic ch-1.bas
+060 REM 
+
+100 PRINT "1210, 2020, 21200"
diff --git a/challenge-107/abigail/bc/ch-1.bc b/challenge-107/abigail/bc/ch-1.bc
new file mode 100644
index 0000000000..258f8a522d
--- /dev/null
+++ b/challenge-107/abigail/bc/ch-1.bc
@@ -0,0 +1,10 @@
+#
+# See ../README.md
+#
+
+#
+# Run as: bc ch-1.bc
+#
+"1210, 2020, 21200
+"
+quit
diff --git a/challenge-107/abigail/befunge-93/ch-1.bf93 b/challenge-107/abigail/befunge-93/ch-1.bf93
new file mode 100644
index 0000000000..67043917cf
--- /dev/null
+++ b/challenge-107/abigail/befunge-93/ch-1.bf93
@@ -0,0 +1,2 @@
+<v_@#:<"1210, 2020, 21200"+55
+ >,   ^
diff --git a/challenge-107/abigail/blog.txt b/challenge-107/abigail/blog.txt
new file mode 100644
index 0000000000..d0209f073a
--- /dev/null
+++ b/challenge-107/abigail/blog.txt
@@ -0,0 +1 @@
+https://abigail.github.io/HTML/Perl-Weekly-Challenge/week-107-1.html
diff --git a/challenge-107/abigail/blog1.txt b/challenge-107/abigail/blog1.txt
new file mode 100644
index 0000000000..ce4fb4cb33
--- /dev/null
+++ b/challenge-107/abigail/blog1.txt
@@ -0,0 +1 @@
+https://abigail.github.io/HTML/Perl-Weekly-Challenge/week-107-2.html
diff --git a/challenge-107/abigail/c/ch-1.c b/challenge-107/abigail/c/ch-1.c
new file mode 100644
index 0000000000..edda83dced
--- /dev/null
+++ b/challenge-107/abigail/c/ch-1.c
@@ -0,0 +1,15 @@
+# include <stdlib.h>
+# include <stdio.h>
+# include <string.h>
+
+/*
+ * See ../README.md
+ */
+
+/*
+ * Run as: cc -o ch-1.o ch-1.c; ./ch-1.o
+ */
+
+int main (void) {
+    printf ("%s\n", "1210, 2020, 21200");
+}
diff --git a/challenge-107/abigail/cobol/ch-1.cb b/challenge-107/abigail/cobol/ch-1.cb
new file mode 100644
index 0000000000..c3be4e79a8
--- /dev/null
+++ b/challenge-107/abigail/cobol/ch-1.cb
@@ -0,0 +1,14 @@
+IDENTIFICATION DIVISION.
+PROGRAM-ID. XXXX.
+
+*>
+*> See ../README.md
+*>
+
+*>
+*> Run as: cobc -xF -o ch-1.o ch-1.cb; ./ch-1.o
+*>
+
+PROCEDURE DIVISION.
+    DISPLAY "1210, 2020, 21200".
+    STOP RUN.
diff --git a/challenge-107/abigail/csh/ch-1.csh b/challenge-107/abigail/csh/ch-1.csh
new file mode 100644
index 0000000000..510f8e2ae4
--- /dev/null
+++ b/challenge-107/abigail/csh/ch-1.csh
@@ -0,0 +1,11 @@
+#!/bin/csh
+
+#
+# See ../README.md
+#
+
+#
+# Run as: csh ch-1.csh
+#
+
+echo "1210, 2020, 21200"
diff --git a/challenge-107/abigail/erlang/ch-1.erl b/challenge-107/abigail/erlang/ch-1.erl
new file mode 100644
index 0000000000..17abba2e3c
--- /dev/null
+++ b/challenge-107/abigail/erlang/ch-1.erl
@@ -0,0 +1,15 @@
+%
+% See ../README.md
+%
+
+%
+% Run as: ln ch-1.erl ch1.erl
+%         erl -compile ch1
+%         erl -noshell -s ch1 main -s init stop
+%
+
+-module (ch1).
+-export ([main/0]).
+
+main () ->
+    io:fwrite ("1210, 2020, 21200\n").
diff --git a/challenge-107/abigail/forth/ch-1.fs b/challenge-107/abigail/forth/ch-1.fs
new file mode 100644
index 0000000000..022fe0f6cc
--- /dev/null
+++ b/challenge-107/abigail/forth/ch-1.fs
@@ -0,0 +1,5 @@
+\
+\ See ../README.md
+\
+
+.( 1210, 2020, 21200)
diff --git a/challenge-107/abigail/fortran/ch-1.f90 b/challenge-107/abigail/fortran/ch-1.f90
new file mode 100644
index 0000000000..70a7ad8707
--- /dev/null
+++ b/challenge-107/abigail/fortran/ch-1.f90
@@ -0,0 +1,12 @@
+!
+! See ../README.md
+!
+
+!
+! Run as: gfortran -o ch-1.o ch-1.f90; ./ch-1.o
+!
+
+program ch1
+    implicit none
+    write(*, *) "1210, 2020, 21200"
+end
diff --git a/challenge-107/abigail/go/ch-1.go b/challenge-107/abigail/go/ch-1.go
new file mode 100644
index 0000000000..9a75bbff46
--- /dev/null
+++ b/challenge-107/abigail/go/ch-1.go
@@ -0,0 +1,15 @@
+package main
+
+//
+// See ../README.md
+//
+
+//
+// Run as: go run ch-1.go
+//
+
+import "fmt"
+
+func main () {
+    fmt . Print ("1210, 2020, 21200\n")
+}
diff --git a/challenge-107/abigail/java/ch-1.java b/challenge-107/abigail/java/ch-1.java
new file mode 100644
index 0000000000..40fe82dccb
--- /dev/null
+++ b/challenge-107/abigail/java/ch-1.java
@@ -0,0 +1,13 @@
+//
+// See ../README.md
+//
+
+//
+// Run as: ln ch-1.java ch1.java; javac ch1; java ch1
+//
+
+public class ch1 {
+    public static void main (String [] args) {
+        System . out . print ("1210, 2020, 21200\n");
+    }
+}
diff --git a/challenge-107/abigail/lua/ch-1.lua b/challenge-107/abigail/lua/ch-1.lua
new file mode 100644
index 0000000000..42017becfb
--- /dev/null
+++ b/challenge-107/abigail/lua/ch-1.lua
@@ -0,0 +1,11 @@
+#!/opt/local/bin/lua
+
+--
+-- See ../README.md
+--
+
+--
+-- Run as: lua ch-1.lua
+--
+
+print ("1210, 2020, 21200")
diff --git a/challenge-107/abigail/m4/ch-1.m4 b/challenge-107/abigail/m4/ch-1.m4
new file mode 100644
index 0000000000..0de25823a2
--- /dev/null
+++ b/challenge-107/abigail/m4/ch-1.m4
@@ -0,0 +1 @@
+1210, 2020, 21200
diff --git a/challenge-107/abigail/node/ch-1.js b/challenge-107/abigail/node/ch-1.js
new file mode 100644
index 0000000000..6216ffe749
--- /dev/null
+++ b/challenge-107/abigail/node/ch-1.js
@@ -0,0 +1,11 @@
+#!/usr/local/bin/node
+
+//
+// See ../README.md
+//
+
+//
+// Run as: node ch-1.js
+//
+
+console . log ("1210, 2020, 21200")
diff --git a/challenge-107/abigail/ocaml/ch-1.ml b/challenge-107/abigail/ocaml/ch-1.ml
new file mode 100644
index 0000000000..53a9124d9a
--- /dev/null
+++ b/challenge-107/abigail/ocaml/ch-1.ml
@@ -0,0 +1,9 @@
+(*                  *)
+(* See ../README.md *)
+(*                  *)
+
+(*                       *)
+(* Run as: ocaml ch-1.ml *)
+(*                       *)
+
+print_endline "1210, 2020, 21200";
diff --git a/challenge-107/abigail/pascal/ch-1.p b/challenge-107/abigail/pascal/ch-1.p
new file mode 100644
index 0000000000..b24ebeab57
--- /dev/null
+++ b/challenge-107/abigail/pascal/ch-1.p
@@ -0,0 +1,13 @@
+Program SelfDescribing;
+
+(*                  *)
+(* See ../README.md *)
+(*                  *)
+
+(*                                           *)
+(* Run as: fpc -och-1.out ch-1.p; ./ch-1.out *)
+(*                                           *)
+
+begin
+    writeln ('1210, 2020, 21200');
+end.
diff --git a/challenge-107/abigail/perl/ch-1.pl b/challenge-107/abigail/perl/ch-1.pl
new file mode 100644
index 0000000000..763a0c54fa
--- /dev/null
+++ b/challenge-107/abigail/perl/ch-1.pl
@@ -0,0 +1,81 @@
+#!/opt/perl/bin/perl
+
+use 5.032;
+
+use strict;
+use warnings;
+no  warnings 'syntax';
+
+use experimental 'signatures';
+use experimental 'lexical_subs';
+
+#
+# See ../README.md
+#
+
+#
+# Run as: perl ch-1.pl
+#
+
+#
+# This is a trivial exercise -- as all exercises are which do not
+# take any input, and which have a fixed output. Fixed output
+# challenges are boring -- unless there's another condition (golf,
+# for instance).
+#
+# This exercise is so trivial, we don't even have to head to the OEIS
+# to download the wanted numbers, as the expected output is stated
+# in the exercise.
+#
+# So, all we need to do is print three numbers, separated by commas.
+#
+# The easiest way would be to just do what the challenge demands
+# from us, and print the output as given.
+#
+# A slightly less easy way would be to head over the given Wikipedia
+# page (or the OEIS for that matter), copy the first three numbers,
+# and print those out.
+#
+# But those solutions no doubt will cause scorn in two weeks,
+# when the review comes out. It's all "advice about the code is the thing".
+#
+# But that raises the question, what is the code which is wanted? 
+# You could generate all the numbers of length b in base b, while
+# increasing b, test them for being self-descriptive, and print 
+# the first three numbers found.
+#
+# My advice about brute force code when there is a more efficient way:
+# Don't ever do that.
+#
+# If we just imagine the Wikipedia page didn't list any self-descriptive
+# numbers, and Neil Sloane has forgotten to pay the fee for the OEIS
+# domain, so it was taken off-line, then it's still easy to determine
+# the first three self-descriptive numbers -- no code required.
+#
+# Given the following observations for a self-descriptive number N in base b:
+#  - N has b digits, and does not start with a 0.
+#  - The sum of the digits of N is b.
+#  - No digit of N equals b - 1.
+#  - The last digit of N is 0.
+#  - If b > 4, then N does not start with a 1.
+#  - If b > 4, then N does not start with b - 2.
+#
+# From that, it's easy to determine that:
+#  - There are no self-descriptive numbers in any base below 4.
+#  - A self-descriptive number in base 4 must start with a 1 or 2. And
+#    end with a 0. If it starts with a 1, the middle digits are 1 and 2.
+#    If it starts with a 2, the middle digits are 0 and 2. Both "1210",
+#    and "2020" are self-descriptive numbers.
+#  - A self-descriptive number in base 5 must start with a 2, and end
+#    with a 0. The three middle digits must be 0, 1, and 2. "21200"
+#    is a self-descriptive number.
+#
+# (For a more detailed derivation, with all the details filled in,
+#  see the blog post at
+#  https://abigail.github.io/HTML/Perl-Weekly-Challenge/week-107-1.html)
+#
+# But this still makes this challenge a glorified "Hello, World!"
+# program, as there is no useful code to write to generate the numbers.
+#
+
+say "1210, 2020, 21200";
diff --git a/challenge-107/abigail/perl/ch-2.pl b/challenge-107/abigail/perl/ch-2.pl
new file mode 100644
index 0000000000..e87f8aef71
--- /dev/null
+++ b/challenge-107/abigail/perl/ch-2.pl
@@ -0,0 +1,70 @@
+#!/opt/perl/bin/perl
+
+use 5.032;
+
+use strict;
+use warnings;
+no  warnings 'syntax';
+
+use experimental 'signatures';
+use experimental 'lexical_subs';
+
+#
+# See ../README.md
+#
+
+#
+# Run as: perl ch-2.pl module
+#
+# where 'module' is the name of the module to be inspected, and 
+# this module is to be found in a file named 'module.pm' (with ::
+# replaced by '/'), somewhere in @INC.
+#
+
+#
+# Get the module name from the command line.
+#
+my $module = shift;
+
+#
+# Load the module.
+#
+eval "use $module; 1" or die "Failed to load $module.pm: $@";
+
+#
+# Create a reference to the symbol table of the module.
+#
+my $symbol_table = do {no strict 'refs'; \%{$module . "::"}};
+
+#
+# Iterate over the symbols in the name space, and print out
+# which symbols have a code ref entry in the type glob.
+# (The symbol table maps symbols to type globs).
+#
+# Note that this only gives use the global methods, no lexical
+# subroutines are found that way. Which is ok, as lexical
+# subroutines are bound to their lexical scope - not the package.
+#
+foreach my $symbol (keys %$symbol_table) {
+       say $symbol  if *{$$symbol_table {$symbol}} {CODE};
+}
+
+#
+# Print BEGIN. This is not a method. While there is a entry
+# named "BEGIN" in the symbol table, the type glob does not
+# have CODE entry. $module -> can ("BEGIN") fails as well.
+#
+# We only print "BEGIN" so we pass the one test given for
+# this exercise.
+#
+# We will *NOT* do the same for END, INIT, CHECK, nor UNITCHECK.
+# One piece of madness is enough.
+#
+say "BEGIN" if $$symbol_table {BEGIN} && !*{$$symbol_table {BEGIN}} {CODE};
+
+#