Merge pull request #6148 from Firedrake/rogerbw-challenge-166

Solutions for challenge #166

17 files changed, 1736 insertions, 0 deletions

diff --git a/challenge-166/roger-bell-west/javascript/ch-1.js b/challenge-166/roger-bell-west/javascript/ch-1.js
new file mode 100755
index 0000000000..6e8f662d3a
--- /dev/null
+++ b/challenge-166/roger-bell-west/javascript/ch-1.js
@@ -0,0 +1,134 @@
+#! /usr/bin/node
+
+function hexwords(lo,hi,sb) {
+    const fs = require("fs")
+    let out = []
+    let buffer = fs.readFileSync("dictionary.txt","utf8")
+    buffer.split(/\r?\n/).forEach(line =>  {
+        if (line.length >= lo && line.length <= hi) {
+            let valid = true
+            let sbc = 0
+            for (let c of line.split("") ) {
+                if (c == 'o' || c == 'i' || c == 'l' || c == 's' || c == 't') {
+                    sbc++
+                    if (sbc > sb) {
+                        valid = false
+                    }
+                } else if (c < 'a' || c > 'f') {
+                    valid = false
+                }
+                if (!valid) {
+                    break
+                }
+            }
+            if (valid) {
+                out.push(line)
+            }
+        }
+    })
+    return out
+}
+
+function combiwords(wl,l) {
+    let wh = new Map()
+    for (let w of wl) {
+        let lw = w.length
+        if (!wh.has(lw)) {
+            wh.set(lw,[])
+        }
+        let t = wh.get(lw)
+        t.push(w)
+        wh.set(lw,t)
+    }
+    let tmap = [[]]
+    let omap = []
+    while (tmap.length > 0) {
+        let c = tmap.pop()
+        let s = c.reduce((x,y) => x+y, 0)
+        for (let j=1; j < l-s; j++) {
+            if (wh.has(j)) {
+                let cc = [...c]
+                cc.push(j)
+                tmap.push(cc)
+            }
+        }
+        if (wh.has(l-s)) {
+            c.push(l-s)
+            omap.push(c)
+        }
+    }
+    let out = []
+    for (let pat of omap) {
+        let c = []
+        let cm = []
+        for (let i of pat) {
+            cm.push(wh.get(i).length-1)
+            c.push(0)
+        }
+        let ex = false
+        while (!ex) {
+            let o = []
+            for (let i = 0; i < c.length; i++) {
+                o.push(wh.get(pat[i])[c[i]])
+            }
+            out.push(o.join(""))
+            let ss = c.length-1
+            while (true) {
+                c[ss]++
+                if (c[ss] > cm[ss]) {
+                    if (ss == 0) {
+                        ex = true
+                        break
+                    }
+                    c[ss] = 0
+                    ss--
+                } else {
+                    break
+                }
+            }
+        }
+    }
+    return out
+}
+
+if (hexwords(2,8,8).length == 1463) {
+    process.stdout.write("Pass")
+} else {
+    process.stdout.write("FAIL")
+}
+process.stdout.write(" ");
+
+if (hexwords(8,8,8).length == 164) {
+    process.stdout.write("Pass")
+} else {
+    process.stdout.write("FAIL")
+}
+process.stdout.write(" ");
+
+if (hexwords(2,8,0).length == 45) {
+    process.stdout.write("Pass")
+} else {
+    process.stdout.write("FAIL")
+}
+process.stdout.write(" ");
+
+if (hexwords(2,8,1).length == 244) {
+    process.stdout.write("Pass")
+} else {
+    process.stdout.write("FAIL")
+}
+process.stdout.write(" ");
+
+if (combiwords(hexwords(4,4,0),8).length == 144) {
+    process.stdout.write("Pass")
+} else {
+    process.stdout.write("FAIL")
+}
+process.stdout.write(" ");
+
+if (combiwords(hexwords(3,5,0),8).length == 274) {
+    process.stdout.write("Pass")
+} else {
+    process.stdout.write("FAIL")
+}
+process.stdout.write("\n");
diff --git a/challenge-166/roger-bell-west/javascript/ch-2.js b/challenge-166/roger-bell-west/javascript/ch-2.js
new file mode 100755
index 0000000000..7380afa1e0
--- /dev/null
+++ b/challenge-166/roger-bell-west/javascript/ch-2.js
@@ -0,0 +1,59 @@
+#! /usr/bin/node
+
+function kdd(dirlist0) {
+    const fs = require("fs")
+    let dirlist = Array.from(dirlist0)
+    dirlist.sort()
+    let fx = new Map()
+    for (let d of dirlist) {
+        for (let entry of fs.readdirSync(d, { withFileTypes: true })) {
+            let nn = entry.name
+            if (entry.isDirectory()) {
+                nn += "/"
+            }
+            if (!fx.has(nn)) {
+                fx.set(nn,new Set())
+            }
+            let t = fx.get(nn)
+            t.add(d)
+            fx.set(nn,t)
+        }
+    }
+    let mm = dirlist.length
+    let out = [dirlist]
+    for (let f of [...fx.keys()].sort()) {
+        if (fx.get(f).size != mm) {
+            let l = []
+            for (let d of dirlist) {
+                if (fx.get(f).has(d)) {
+                    l.push(f)
+                } else {
+                    l.push("")
+                }
+            }
+            out.push(l)
+        }
+    }
+    tabular(out)
+}
+
+function tabular(d) {
+    let columnlength = []
+    d.forEach(row => {
+        row.forEach((col, i) => {
+            while (columnlength.length <= i) {
+                columnlength.push(0)
+            }
+            columnlength[i] = Math.max(columnlength[i], col.length)
+        })
+    })
+    d.forEach(row => {
+        let s = []
+        row.forEach((col, i) => {
+            s.push(col.padEnd(columnlength[i]))
+        })
+        console.log(s.join(" | "))
+    })
+}
+    
+kdd(["dir_a","dir_b","dir_c"])
diff --git a/challenge-166/roger-bell-west/kotlin/ch-1.kt b/challenge-166/roger-bell-west/kotlin/ch-1.kt
new file mode 100644
index 0000000000..c391716661
--- /dev/null
+++ b/challenge-166/roger-bell-west/kotlin/ch-1.kt
@@ -0,0 +1,133 @@
+import kotlin.io.*
+
+fun hexwords(lo: Int, hi: Int, sb: Int): List<String> {
+    var out = ArrayList<String>()
+    java.io.File("dictionary.txt").forEachLine { line ->
+                                                     if (line.length >= lo && line.length <= hi) {
+                                                         var valid = true
+                                                         var sbc = 0
+                                                         for (c in line.toCharArray().toList()) {
+                                                             if (c == 'o' || c == 'i' || c == 'l' || c == 's' || c == 't') {
+                                                                 sbc += 1
+                                                                 if (sbc > sb) {
+                                                                     valid = false
+                                                                 }
+                                                             } else if (c < 'a' || c > 'f') {
+                                                                 valid = false
+                                                             }
+                                                             if (!valid) {
+                                                                 break
+                                                             }
+                                                         }
+                                                         if (valid) {
+                                                             out.add(line)
+                                                         }
+                                                     }
+    }
+    return out
+}
+
+fun combiwords(wl: List<String>, l: Int): List<String> {
+    var wh = mutableMapOf<Int,ArrayList<String>>()
+    for (w in wl) {
+        if (!wh.containsKey(w.length)) {
+            wh[w.length] = ArrayList<String>()
+        }
+        wh[w.length]!!.add(w)
+    }
+    var tmap = ArrayList<ArrayList<Int>>()
+    tmap.add(ArrayList<Int>())
+    var omap = ArrayList<ArrayList<Int>>()
+    while (tmap.size > 0) {
+        var c = tmap.removeLast()
+        val s = c.sum()
+        val ls = l - s
+        for (j in 1..ls-1) {
+            if (wh.containsKey(j)) {
+                var cc = ArrayList(c)
+                cc.add(j)
+                tmap.add(cc)
+            }
+        }
+        if (wh.containsKey(ls)) {
+            c.add(ls)
+            omap.add(c)
+        }
+    }
+    var out = ArrayList<String>()
+    for (pat in omap) {
+        var c = ArrayList<Int>()
+        var cm = ArrayList<Int>()
+        for (i in pat) {
+            cm.add(wh[i]!!.size-1)
+            c.add(0)
+        }
+        var ex = false
+        while (!ex) {
+            var o = ArrayList<String>()
+            for (i in 0..c.size-1) {
+                o.add(wh[pat[i]]!![c[i]])
+            }
+            out.add(o.joinToString(""))
+            var ss = c.size-1
+            while (true) {
+                c[ss] += 1
+                if (c[ss] > cm[ss]) {
+                    if (ss == 0) {
+                        ex = true
+                        break
+                    }
+                    c[ss] = 0
+                    ss--
+                } else {
+                    break
+                }
+            }
+        }
+    }
+    return out
+}
+
+fun main() {
+    if (hexwords(2,8,8).size == 1463) {
+        print("Pass")
+    } else {
+        print("FAIL")
+    }
+    print(" ")
+    
+    if (hexwords(8,8,8).size == 164) {
+        print("Pass")
+    } else {
+        print("FAIL")
+    }
+    print(" ")
+    
+    if (hexwords(2,8,0).size == 45) {
+        print("Pass")
+    } else {
+        print("FAIL")
+    }
+    print(" ")
+
+    if (hexwords(2,8,1).size == 244) {
+        print("Pass")
+    } else {
+        print("FAIL")
+    }
+    print(" ")
+
+    if (combiwords(hexwords(4,4,0),8).size == 144) {
+        print("Pass")
+    } else {
+        print("FAIL")
+    }
+    print(" ")
+
+    if (combiwords(hexwords(3,5,0),8).size == 274) {
+        print("Pass")
+    } else {
+        print("FAIL")
+    }
+    println("")
+}
diff --git a/challenge-166/roger-bell-west/kotlin/ch-2.kt b/challenge-166/roger-bell-west/kotlin/ch-2.kt
new file mode 100644
index 0000000000..b69f6eb44f
--- /dev/null
+++ b/challenge-166/roger-bell-west/kotlin/ch-2.kt
@@ -0,0 +1,55 @@
+import kotlin.io.*
+import kotlin.math.max
+
+fun kdd(dirlist0: ArrayList<String>): ArrayList<ArrayList<String>> {
+    val dirlist = ArrayList(dirlist0.sorted())
+    var fx = mutableMapOf<String,MutableSet<String>>()
+    for (d in dirlist) {
+        java.io.File(d).listFiles().forEach() { entry ->
+                                                    var nn = entry.getName()
+                                                if (entry.isDirectory()) {
+                                                    nn += "/"
+                                                }
+                                                if (!fx.containsKey(nn)) {
+                                                    fx[nn] = mutableSetOf<String>()
+                                                }
+                                                fx[nn]!!.add(d)
+        }
+    }
+    val mm = dirlist.size
+    var out = arrayListOf(dirlist)
+    for (f in fx.keys.sorted()) {
+        if (fx[f]!!.size != mm) {
+            var l = arrayListOf<String>()
+            for (d in dirlist) {
+                if (fx[f]!!.contains(d)) {
+                    l.add(f)
+                } else {
+                    l.add("")
+                }
+            }
+            out.add(l)
+        }
+    }
+    return(out)
+}
+
+fun tabular(d: ArrayList<ArrayList<String>>) {
+    var columnlength = ArrayList<Int>()
+    for (row in d) {
+        row.forEachIndexed {i,col ->
+                                while (columnlength.size <= i) {
+                                    columnlength.add(0)
+                                }
+                            columnlength[i] = max(columnlength[i],col.length)
+        }
+    }
+    val fstr=columnlength.map {l -> "%-" + l.toString() + "s"}.joinToString(" | ")
+    for (row in d) {
+        println(fstr.format(*row.toTypedArray()))
+    }
+}
+
+fun main() {
+    tabular(kdd(arrayListOf<String>("dir_a","dir_b","dir_c")))
+}
diff --git a/challenge-166/roger-bell-west/lua/ch-1.lua b/challenge-166/roger-bell-west/lua/ch-1.lua
new file mode 100755
index 0000000000..4b7858db3c
--- /dev/null
+++ b/challenge-166/roger-bell-west/lua/ch-1.lua
@@ -0,0 +1,144 @@
+#! /usr/bin/lua
+
+function join(t)
+   local out=""
+   for k,v in pairs(t) do
+      out = out .. v
+   end
+   return out
+end
+
+function hexwords(lo,hi,sb)
+   local out = {}
+   for line in io.lines("dictionary.txt") do
+      if #line >= lo and #line <= hi then
+         local valid = true
+         local sbc = 0
+         for i = 1,#line do
+            local c = string.sub(line,i,i)
+            if c == "o" or c == "i" or c == "l" or c == "s" or c == "t" then
+               sbc = sbc + 1
+               if sbc > sb then
+                  valid = false
+               end
+            elseif c < "a" or c > "f" then
+               valid = false
+            end
+            if not valid then
+               break
+            end
+         end
+         if valid then
+            table.insert(out,line)
+         end
+      end
+   end
+   return out
+end
+
+function combiwords(wl,l)
+   local wh = {}
+   for k,w in pairs(wl) do
+      if wh[#w] == nil then
+         wh[#w] = {}
+      end
+      table.insert(wh[#w],w)
+   end
+   local tmap = { {} }
+   local omap = {}
+   while #tmap > 0 do
+      local c = table.remove(tmap)
+      local s = 0
+      for k,x in pairs(c) do
+         s = s + x
+      end
+      for j = 1, l-s-1 do
+         if wh[j] ~= nil then
+            local cc = {}
+            for k,x in pairs(c) do
+               table.insert(cc,x)
+            end
+            table.insert(cc,j)
+            table.insert(tmap,cc)
+         end
+      end
+      if wh[l-s] ~= nil then
+         table.insert(c,l-s)
+         table.insert(omap,c)
+      end
+   end
+   local out = {}
+   for k,pat in pairs(omap) do
+      local c = {}
+      local cm = {}
+      for kk,i in pairs(pat) do
+         table.insert(cm,#wh[i])
+         table.insert(c,1)
+      end
+      local ex = false
+      while not ex do
+         local o = {}
+         for i = 1,#c do
+            table.insert(o,wh[pat[i]][c[i]])
+         end
+         table.insert(out,join(o,""))
+         local ss = #c
+         while true do
+            c[ss] = c[ss] + 1
+            if c[ss] > cm[ss] then
+               if ss == 1 then
+                  ex = true
+                  break
+               end
+               c[ss] = 1
+               ss = ss - 1
+            else
+               break
+            end
+         end
+      end
+   end
+   return out
+end
+
+if #hexwords(2,8,8) == 1463 then
+   io.write("Pass")
+else
+   io.write("FAIL")
+end
+io.write(" ")
+
+if #hexwords(8,8,8) == 164 then
+   io.write("Pass")
+else
+   io.write("FAIL")
+end
+io.write(" ")
+
+if #hexwords(2,8,0) == 45 then
+   io.write("Pass")
+else
+   io.write("FAIL")
+end
+io.write(" ")
+
+if #hexwords(2,8,1) == 244 then
+   io.write("Pass")
+else
+   io.write("FAIL")
+end
+io.write(" ")
+
+if #combiwords(hexwords(4,4,0),8) == 144 then
+   io.write("Pass")
+else
+   io.write("FAIL")
+end
+io.write(" ")
+
+if #combiwords(hexwords(3,5,0),8) == 274 then
+   io.write("Pass")
+else
+   io.write("FAIL")
+end
+print("")
diff --git a/challenge-166/roger-bell-west/perl/ch-1.pl b/challenge-166/roger-bell-west/perl/ch-1.pl
new file mode 100755
index 0000000000..a87a976310
--- /dev/null
+++ b/challenge-166/roger-bell-west/perl/ch-1.pl
@@ -0,0 +1,98 @@
+#! /usr/bin/perl
+
+use strict;
+use warnings;
+
+use experimental 'signatures';
+
+use List::Util qw(sum0);
+
+use Test::More tests => 6;
+
+is(scalar @{hexwords(2,8,8)},1463,'example 1');
+
+is(scalar @{hexwords(8,8,8)},164,'example 2');
+
+is(scalar @{hexwords(2,8,0)},45,'example 3');
+
+is(scalar @{hexwords(2,8,1)},244,'example 4');
+
+is(scalar @{combiwords(hexwords(4,4,0),8)},144,'example 5');
+
+is(scalar @{combiwords(hexwords(3,5,0),8)},274,'example 6');
+
+sub hexwords($lo,$hi,$sb) {
+  my @out;
+  open my $fh,'<','dictionary.txt';
+  while (my $line = <$fh>) {
+    chomp $line;
+    if (length($line) >= $lo && length($line) <= $hi) {
+      my $valid = 1;
+      my $sbc = 0;
+      foreach my $c (split '',$line) {
+        if ($c =~ /[oilst]/) {
+          $sbc++;
+          if ($sbc > $sb) {
+            $valid = 0;
+          }
+        } elsif ($c lt 'a' || $c gt 'f') {
+          $valid = 0;
+        }
+        unless ($valid) {
+          last;
+        }
+      }
+        if ($valid) {
+          push @out,$line;
+        }
+    }
+  }
+  close $fh;
+  return \@out;
+}
+
+sub combiwords($wl,$l) {
+  my %wh;
+  foreach my $w (@{$wl}) {
+    push @{$wh{length($w)}},$w;
+  }
+  my @tmap=([]);
+  my @omap;
+  while (scalar @tmap > 0) {
+    my $c=pop @tmap;
+    my $s=sum0(@{$c});
+    my $ls=$l-$s;
+    foreach my $j (1..$ls-1) {
+      if (exists $wh{$j}) {
+        push @tmap,[@{$c},$j];
+      }
+    }
+    if (exists $wh{$ls}) {
+      push @omap,[@{$c},$ls];
+    }
+  }
+  my @out;
+  foreach my $pat (@omap) {
+    my @c = (0) x (scalar @{$pat});
+    my @cm = map {scalar @{$wh{$pat->[$_]}}-1} (0..$#c);
+    my $ex = 0;
+    while (!$ex) {
+      push @out,join('',map {$wh{$pat->[$_]}->[$c[$_]]} (0..$#c));
+      my $ss = $#c;
+      while (1) {
+        $c[$ss]++;
+        if ($c[$ss] > $cm[$ss]) {
+          if ($ss == 0) {
+            $ex = 1;
+            last;
+          }
+          $c[$ss] = 0;
+          $ss--;
+        } else {
+          last;
+        }
+      }
+    }
+  }
+  return \@out;
+}
diff --git a/challenge-166/roger-bell-west/perl/ch-2.pl b/challenge-166/roger-bell-west/perl/ch-2.pl
new file mode 100755
index 0000000000..d5e7ea52e6
--- /dev/null
+++ b/challenge-166/roger-bell-west/perl/ch-2.pl
@@ -0,0 +1,59 @@
+#! /usr/bin/perl
+
+use strict;
+use warnings;
+
+use experimental 'signatures';
+
+sub kdd(@dirlist0) {
+  my @dirlist = sort @dirlist0;
+  my %fx;
+  foreach my $d (@dirlist) {
+    opendir (my $dh,$d);
+    foreach my $entry (grep !/^\./,readdir $dh) {
+      my $nn = $entry;
+      if (-d "$d/$entry") {
+        $nn .= '/';
+      }
+      $fx{$nn}{$d} = 1;
+    }
+    closedir $dh;
+  }
+  my $mm=scalar @dirlist;
+  my @out=(\@dirlist);
+  foreach my $f (sort keys %fx) {
+    unless (scalar keys %{$fx{$f}} == $mm) {
+      my @l;
+      foreach my $d (@dirlist) {
+        if (exists $fx{$f}{$d}) {
+          push @l,$f;
+        } else {
+          push @l,'';
+        }
+      }
+      push @out,\@l;
+    }
+  }
+  return \@out;
+}
+
+
+sub tabular($d) {
+  my @columnlength;
+  foreach my $row (@{$d}) {
+    foreach my $colno (0..$#{$row}) {
+      if (!defined($columnlength[$colno]) ||
+          $columnlength[$colno] < length($row->[$colno])) {
+        $columnlength[$colno]=length($row->[$colno]);
+      }
+    }
+  }
+  my $format=join(' | ',map {"%-${_}s"} @columnlength);
+  my $result='';
+  foreach my $row (@{$d}) {
+    $result .= sprintf($format,@{$row})."\n";
+  }
+  return $result;
+}
+
+print tabular(kdd("dir_a","dir_b","dir_c"));
diff --git a/challenge-166/roger-bell-west/postscript/ch-1.ps b/challenge-166/roger-bell-west/postscript/ch-1.ps
new file mode 100644
index 0000000000..3fed3b9fe5
--- /dev/null
+++ b/challenge-166/roger-bell-west/postscript/ch-1.ps
@@ -0,0 +1,263 @@
+%!PS
+
+/test {
+    /test.count test.count 1 add def
+    {
+        /test.pass test.pass 1 add def
+    } {
+        ( ) print
+        test.count (....) cvs print
+        (-fail) print
+    } ifelse
+} bind def
+
+/test.start {
+    print (:) print
+    /test.pass 0 def
+    /test.count 0 def
+} bind def
+
+/test.end {
+    ( ) print
+    test.count 0 gt {
+        (Passed ) print
+        test.pass (...) cvs print
+        (/) print
+        test.count (...) cvs print
+        ( \() print
+        test.pass 100 mul test.count idiv (...) cvs print
+        (%\)) print
+        (\r\n) print
+    } if
+} bind def
+
+/apush.right { % [a b] c -> [a b c]
+    exch
+    [ exch aload length 2 add -1 roll ]
+} bind def
+
+/apop.right { % [a b c] -> [a b] c
+    [ exch aload length 1 add 1 roll ] exch
+} bind def
+
+/keys { % dict -> array of dict keys
+    [ exch
+      {
+          pop
+      } forall
+    ]
+} bind def
+
+/filter { % array proc(bool) -> array
+    1 dict begin
+    /p exch def
+    [ exch
+      {
+          dup p not
+          {
+              pop
+          } if
+      } forall
+    ]
+    end
+} bind def
+
+/reduce_init { % value array proc -> value
+    2 dict begin
+    /p exch def
+    /a exch def
+    0 1 a length 1 sub {
+        a exch get
+        p
+    } for
+    end
+} bind def
+
+/strconcat % (a) (b) -> (ab)  
+{ exch dup length
+  2 index length add string
+  dup dup 4 2 roll copy length
+  4 -1 roll putinterval
+} bind def
+
+/strjoin % [(a) (b) (c)] (j) -> (ajbjc)
+{
+    3 dict begin
+    /j exch def
+    dup 0 get /out exch def
+    /first true def
+    {
+        first {
+            pop
+            /first false def
+        } {
+            out j strconcat
+            exch strconcat
+            /out exch def
+        } ifelse
+    } forall
+    out
+    end
+} bind def
+
+/strsplit % (ajbjc) (j) -> [ (a) (b) (c) ]
+{
+    1 dict begin
+    /sep exch def
+    [ exch
+      {
+          dup length 0 eq {
+              pop
+              exit
+          } {
+              sep search {
+                  exch pop
+                  dup length 0 eq {
+                      pop
+                  } {
+                      exch
+                  } ifelse
+              } {
+                  ()
+              } ifelse
+          } ifelse
+      } loop
+    ]
+    end
+} bind def
+
+/cartesianproduct { % [ [ a b ] [ c d ] ] -> [ [ a c ] [ a d ] [ b c ] [ b d ] ]
+    5 dict begin
+    /pat exch def
+    /c [ pat length { 0 } repeat ] def
+    /cm [ pat { length 1 sub } forall ] def 
+    /ex false def
+    [
+        {
+            ex {
+                exit
+            } if
+            [
+                0 1 c length 1 sub {
+                    /i exch def
+                    pat i get c i get get
+                } for
+            ]
+            /ss c length 1 sub def
+            {
+                c ss c ss get 1 add put
+                c ss get cm ss get gt {
+                    ss 0 eq {
+                        /ex true def
+                        exit
+                    } if
+                    c ss 0 put
+                    /ss ss 1 sub def
+                } {
+                    exit
+                } ifelse
+            } loop
+        } loop
+        end
+    ]
+} bind def
+
+/hexwords {
+    7 dict begin
+    /sb exch def
+    /hi exch def
+    /lo exch def
+    /abcdef (abcdef) def
+    /oilst (oilst) def
+    [
+        (dictionary.txt) (r) file dup bytesavailable string readstring pop
+        (\n) strsplit {
+            dup length dup lo ge exch hi le and {
+                /valid true def
+                /sbc 0 def
+                dup {
+                    (.) dup 0 3 index put exch pop
+                    dup oilst exch search {
+                        pop pop pop pop
+                        /sbc sbc 1 add def
+                        sbc sb gt {
+                            /valid false def
+                        } if
+                    } {
+                        pop
+                        abcdef exch search {
+                            pop pop pop
+                        } {
+                            pop
+                            /valid false def
+                        } ifelse
+                    } ifelse
+                    valid not {
+                        exit
+                    } if
+                } forall
+                valid not {
+                    pop
+                } if
+            } {
+                pop
+            } ifelse
+        } forall
+    ]
+    end
+} bind def
+
+/combiwords {
+    7 dict begin
+    /l exch def
+    /wh 0 dict def
+    {
+        dup length /lx exch def
+        wh lx known not {
+            wh lx 0 array put
+        } if
+        wh lx get exch apush.right wh exch lx exch put
+    } forall
+    /tmap [ 0 array ] def
+    /omap 0 array def
+    {
+        tmap length 0 eq {
+            exit
+        } if
+        tmap apop.right /c exch def /tmap exch def
+        /s 0 c { add } reduce_init def
+        1 1 l s sub {
+            /j exch def
+            wh j known {
+                /tmap tmap c j apush.right apush.right def
+            } if
+        } for
+        wh l s sub known {
+            /omap omap c l s sub apush.right apush.right def
+        } if
+    } loop
+    [
+        omap {
+            [ exch
+              { wh exch get } forall
+            ]
+            cartesianproduct
+            {
+                () strjoin
+            } forall
+        } forall
+    ]
+    end
+} bind def
+
+(hexwords) test.start
+2 8 8 hexwords length 1463 eq test
+8 8 8 hexwords length 164 eq test
+2 8 0 hexwords length 45 eq test
+2 8 1 hexwords length 244 eq test
+test.end
+
+(combiwords) test.start
+4 4 0 hexwords 8 combiwords length 144 eq test
+3 5 0 hexwords 8 combiwords length 274 eq test
+test.end
diff --git a/challenge-166/roger-bell-west/postscript/ch-2.ps b/challenge-166/roger-bell-west/postscript/ch-2.ps
new file mode 100644
index 0000000000..46dac29cb2
--- /dev/null
+++ b/challenge-166/roger-bell-west/postscript/ch-2.ps
@@ -0,0 +1,206 @@
+%! PS
+
+/quicksort { % [ a c b ] -> [ a b c ]
+    1 dict begin
+    /arr exch def
+    0 arr length 1 sub quicksort.main
+    arr
+    end
+} bind def
+
+/quicksort.main { % lo hi -> (null)
+    3 dict begin
+    /hi exch def
+    /lo exch def
+    /xit false def
+    lo 0 lt {
+        /xit true def
+    } if
+    hi 0 lt {
+        /xit true def
+    } if
+    lo hi ge {
+        /xit true def
+    } if
+    xit not {
+        /p quicksort.partition def
+        lo p quicksort.main
+        p 1 add hi quicksort.main
+    } if
+    end
+} bind def
+
+/quicksort.partition {
+    3 dict begin
+    /pivot arr hi lo add 2 idiv get def
+    /i lo 1 sub def
+    /j hi 1 add def
+    {
+        {
+            /i i 1 add def
+            arr i get pivot ge {
+                exit
+            } if
+        } loop
+        {
+            /j j 1 sub def
+            arr j get pivot le {
+                exit
+            } if
+        } loop
+        i j ge {
+            j
+            exit
+        } if
+        i j quicksort.swap