1 files changed, 248 insertions, 0 deletions
diff --git a/2-the-false-awakens/remarks.markdown b/2-the-false-awakens/remarks.markdown
new file mode 100644
index 0000000..7f072a9
--- /dev/null
+++ b/2-the-false-awakens/remarks.markdown
@@ -0,0 +1,248 @@
+# Episode VII: The False Awakens
+
+> A long time ago in a galaxy far,
+> far away....
+
+
+
+
+## Remarks
+
+Just run it with:
+
+```
+$ ruby entry.rb
+```
+
+It will output "TRICK 2025".
+
+It has been tested under the following environment:
+
+```
+$ ruby --version
+ruby 3.4.1 (2024-12-25 revision 48d4efcb85) +PRISM [x86_64-linux]
+```
+
+
+
+## Description
+
+The program consists of two parts:
+
+* an interpreter of a subset of [FALSE esolang](https://esolangs.org/wiki/FALSE) and
+* an obfuscated FALSE source code.
+
+### FALSE interpreter
+
+The interpreter part is embeeded into an ASCII art, "TRICK 2025" shaped like the Star Wars logo.
+For more readable version, see `entry.clean.rb`.
+
+### FALSE source code
+
+The FALSE source code is encoded to the following expression:
+
+```
+  TrUE&FaLsE|TrUe&FaLse|TrUe&FAlSe|TrUE&FalSE|TrUe&FAlSe|TrUe&FaLse|TrUe&FaLse|TrUe&FaLse|TrUe&FaLse|TrUE&FAlsE|TrUe&FAlSE|TrUe&FALse|
+  TrUE&FaLsE|TrUe&FAlSE|TrUe&FALse|TrUE&FalSe|TrUe&FALsE|TrUe&FALse|TrUE&FAlse|TrUe&FALsE|TrUe&FALse|TrUe&FALse|TrUE&FaLse|TrUE&FAlse|
+  TrUe&FAlSe|TrUe&FALse|TrUE&FaLsE|TrUE&FalSe|TrUE&False|TrUE&FalSe|TrUe&FALSe|TrUe&FALSe|TrUe&FALSe|TrUe&FALSe|TrUE&FalSe|TrUE&FaLsE|
+  TrUe&FAlSe|TrUe&FALse|false
+```
+
+Decoded version:
+
+```
+5$*3*$$$$9+,7+,2-,8-,,48*,5202....25*,
+```
+
+FALSE is a simple stack-based esolang. For instance,
+
+* `5` pushes 5: `[5]`
+* `$` duplicates the top: `[5 5]`
+* `*` pushes the product: `[25]`
+* `3` pushes 3: `[25 3]`
+* `*` pushes the product: `[75]`
+* `$$$$` duplicates the top 4 times: `[75 75 75 75 75]`
+* `9` pushes 9: `[75 75 75 75 75 9]`
+* `+` pushes the sum: `[75 75 75 75 84]`
+* `,` writes the character: `[75 75 75 75]` (output `T`)
+* `7` pushes 9: `[75 75 75 75 7]`
+* `+` pushes the sum: `[75 75 75 82]`
+* `,` writes the character: `[75 75 75]` (output `R`)
+* ...
+
+
+The source code is full of Star Wars references and homages.
+
+
+```
+# A long time ago in a galaxy far,
+# far away....
+```
+
+This is the iconic Star Wars opening phrase.
+
+```
+# (inside the eval'ed code)
+
+  while(c<p.size);
+    if(!(i=p[c]));false;
+    elsif"$"==i;s.push(s.last);
+    elsif"%"==i;s.pop;
+    ...
+```
+
+All comparison operations used in the program are written in the so-called "Yoda notation" (placing constants on the left hand side), referencing the Jedi Master Yoda.
+
+
+```
+     EPISODE_VII
+
+  THE_FALSE_AWAKENS
+```
+
+This parodies the Star Wars Episode VII subtitle, "The Force Awakens."
+"Force" refers to a supernatural power in Star Wars, but for our program, "false" has awakened instead because we used many `false`s.
+
+
+```
+  May.the.false.be.with.you;
+```
+
+This is a twist on one of the most famous Star Wars lines, "May the Force be with you."
+
+
+
+
+## Internals
+
+### FALSE interpreter
+
+The interepreter is implemented as a method named `false`. In Ruby, you can use keywords as method names like this. It cannot be invoked directly, but you can call such a method via explicit receiver:`self.false()`
+
+
+### Encoding the FALSE program
+
+The FALSE program is obfuscated like this:
+
+```
+  TrUE&FaLsE|TrUe&FaLse|TrUe&FAlSe|TrUE&FalSE|TrUe&FAlSe|TrUe&FaLse|TrUe&FaLse|TrUe&FaLse|TrUe&FaLse|TrUE&FAlsE|TrUe&FAlSE|TrUe&FALse|
+  TrUE&FaLsE|TrUe&FAlSE|TrUe&FALse|TrUE&FalSe|TrUe&FALsE|TrUe&FALse|TrUE&FAlse|TrUe&FALsE|TrUe&FALse|TrUe&FALse|TrUE&FaLse|TrUE&FAlse|
+  TrUe&FAlSe|TrUe&FALse|TrUE&FaLsE|TrUE&FalSe|TrUE&False|TrUE&FalSe|TrUe&FALSe|TrUe&FALSe|TrUe&FALSe|TrUe&FALSe|TrUE&FalSe|TrUE&FaLsE|
+  TrUe&FAlSe|TrUe&FALse|false
+```
+
+Each segment separated by `|` represents one instruction.
+
+* `TrUE&FaLsE` => `5`
+* `TrUe&FaLse` => `$`
+* `TrUe&FAlSe` => `*`
+* ...
+
+This is achieved by defining `Object.const_missing`, `String#&`, and `String#|`.
+
+First, our `const_missing `dynamically defines constants like `TrUE`:
+
+```
+# (inside the eval'ed code)
+
+def Object.const_missing(n);
+  const_set(n,n.to_s);
+end;
+```
+
+With that, constant `TrUE` is resolved to string `"TrUE"`.
+
+Second, such strings are concatenated with `&` with special decoding:
+
+```
+# (inside the eval'ed code)
+
+class'String;
+  def&(other);
+    (self[1..]+other[1..])
+      .chars
+      .map{(_1.upcase==_1)??1:?0}
+      .join
+      .to_i(2)
+      .chr;
+  end;
+end;
+```
+
+For `TrUE & FaLsE`,
+
+```
+    (self[1..]+other[1..])              # => "rUEaLsE"
+      .chars                            # => ["r","U","E","a","L","s","E"]
+      .map{(_1.upcase==_1)??1:?0}       # => ["0","1","1","0","1","0","1"]
+      .join                             # => "0110101"
+      .to_i(2)                          # => 53
+      .chr;                             # => "5"
+```
+
+Finally, each FALSE instruction is concatenated by `|` operator:
+
+```
+# (inside the eval'ed code)
+
+class'String;
+  def|(other);
+    (self||"")+(other||"");
+  end;
+end;
+```
+
+
+# Misc.
+
+```
+     EPISODE_VII
+
+  THE_FALSE_AWAKENS
+```
+
+This code is equivalent to this:
+
+```
+     "EPISODE_VII"
+
+  "THE_FALSE_AWAKENS"
+```
+
+It does nothing.
+
+```
+  May.the.false.be.with.you;
+```
+
+`May` is resolved to string `"May"` and the rest method chain is dispatched to `String#method_missing` defined here:
+
+```
+# (inside the eval'ed code)
+
+class'String;
+  def'method_missing(_);
+    self;
+  end;
+end;
+```
+
+It does nothing too.
+
+
+
+
+
+## Limitations
+
+Our FALSE interpreter does not support the following instructions:
+
+* `'c`: literal character "c"
+* `ø`: pick
+* `^`: input
+* `"string"`: output "string"
+* `ß`: flush the inout/output buffer.
+* `{...}`: comments
+* `\``: compile
+
+Also, only one-digit numeric literals are supported, so `123` is interpreted as pushing `1`, `2` and `3` separately.