From bfed3dfba46a3f39389bdb529e021e266128df67 Mon Sep 17 00:00:00 2001
From: Nat Lasseter <Nat Lasseter user@4574.co.uk>
Date: Thu, 15 Feb 2018 14:50:59 +0000
Subject: Initial Commit

---
 parse.rb       | 44 ++++++++++++++++++++++++++++++++++++++++++++
 patter.rb      | 43 +++++++++++++++++++++++++++++++++++++++++++
 readme.textile | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 test.pr        | 37 +++++++++++++++++++++++++++++++++++++
 4 files changed, 170 insertions(+)
 create mode 100644 parse.rb
 create mode 100644 patter.rb
 create mode 100644 readme.textile
 create mode 100644 test.pr

diff --git a/parse.rb b/parse.rb
new file mode 100644
index 0000000..5fcfad2
--- /dev/null
+++ b/parse.rb
@@ -0,0 +1,44 @@
+def sub_vars(string)
+  outvars = []
+  blockvars = []
+  vars = string.split(",").map(&:strip)
+  vars.each do |var|
+    if var =~ /[a-z_][a-zA-Z0-9_]*?/ then
+      outvars << "Patter::Var"
+      blockvars << var
+    else
+      outvars << var
+    end
+  end
+  return outvars.join(", "), blockvars.join(", ")
+end
+
+def sub_funs(string, funs)
+  funs.each do |fun|
+    string.gsub!(/#{fun}\((.*?)\)/, "#{fun}.call(\\1)")
+  end
+  return string
+end
+
+lines = $stdin.readlines.map(&:chomp)
+funs = []
+
+puts "require './patter'"
+puts
+
+lines.each do |line|
+  if line =~ /\s*([a-z_][a-zA-Z0-9_]*?)\((.*)\) is\s*$/ then
+    unless funs.include?($1) then
+      funs << $1
+      puts "#{$1} = Patter::Fun.new"
+    end
+    arg, blk = sub_vars($2)
+    if blk.empty? then
+      puts "#{$1}.when(#{arg}) do"
+    else
+      puts "#{$1}.when(#{arg}) do |#{blk}|"
+    end
+  else
+    puts sub_funs(line, funs)
+  end
+end
diff --git a/patter.rb b/patter.rb
new file mode 100644
index 0000000..348cbdf
--- /dev/null
+++ b/patter.rb
@@ -0,0 +1,43 @@
+module Patter
+  class Var; end
+
+  class Fun
+    def initialize
+      @patterns = {}
+    end
+
+    def when(*args, &block)
+      raise "Block arity does not match number of free variables" if args.count(Var) != block.arity
+      @patterns[args] = block
+    end
+
+    def call(*args)
+      free_vars, block = match(args)
+      block.call(*free_vars)
+    end
+
+    alias_method :[], :call
+
+    private
+
+    def match(args)
+      @patterns.each do |pattern, block|
+        next if pattern.length != args.length
+        free_variables = []
+        matched = true
+        pattern.zip(args).each do |pair|
+          if pair.first == Var then
+            free_variables << pair.last
+            next
+          end
+          if pair.first != pair.last then
+            matched = false
+            break
+          end
+        end
+        return [free_variables, block] if matched
+      end
+      raise "Inexhaustive patterns"
+    end
+  end
+end
diff --git a/readme.textile b/readme.textile
new file mode 100644
index 0000000..a5c25f2
--- /dev/null
+++ b/readme.textile
@@ -0,0 +1,46 @@
+h1. Patter
+
+This is Patter(n Ruby).
+
+h2. What?
+
+It's a pattern matching thing for Ruby. It's AWFUL.
+
+h2. How?
+
+h3. Patter macro parser
+
+bc.. $ echo <<. >test.pr
+fib(0) is
+  1
+end
+fib(1) is
+  1
+end
+fib(x) is
+  fib(x-1) + fib(x-2)
+end
+
+puts fib(10)
+.
+$ ruby parse.rb <test.pr >test.rb
+$ ruby test.rb
+
+h3. Include Patter
+
+bc.. $ echo <<. >test.rb
+require './patter'
+include Patter
+
+fib = Fun.new
+fib.when(0){1}
+fib.when(1){1}
+fib.when(Var) do |n|
+  fib.call(n-1) + fib.call(n-2)
+end
+.
+$ ruby test.rb
+
+h2. Why?
+
+Clearly the Eldritch horrors are upon us.
diff --git a/test.pr b/test.pr
new file mode 100644
index 0000000..77dfb27
--- /dev/null
+++ b/test.pr
@@ -0,0 +1,37 @@
+zerop(0) is
+  true
+end
+zerop(_) is
+  false
+end
+
+fib(0) is
+  1
+end
+fib(1) is
+  1
+end
+fib(x) is
+  fib(x-1) + fib(x-2)
+end
+
+add(x, y) is
+  x + y
+end
+
+puts add(1, 2)
+puts fib(5)
+
+putser(string) is
+  puts string
+end
+putser("foo")
+
+varity(_) is
+  puts "one thing"
+end
+varity(_, _) is
+  puts "two things"
+end
+varity(1)
+varity(1,2)
-- 
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