2 files changed, 116 insertions, 0 deletions
diff --git a/ruby/step5_tco.rb b/ruby/step5_tco.rb
new file mode 100644
index 0000000..8eb73c8
--- /dev/null
+++ b/ruby/step5_tco.rb
@@ -0,0 +1,98 @@
+require "readline"
+require "types"
+require "reader"
+require "printer"
+require "env"
+require "core"
+
+# read
+def READ(str)
+    return read_str(str)
+end
+
+# eval
+def eval_ast(ast, env)
+    return case ast
+        when Symbol
+            env.get(ast)
+        when List   
+            List.new ast.map{|a| EVAL(a, env)}
+        when Vector
+            Vector.new ast.map{|a| EVAL(a, env)}
+        else 
+            ast
+    end
+end
+
+def EVAL(ast, env)
+    while true
+
+    if not ast.is_a? List
+        return eval_ast(ast, env)
+    end
+
+    # apply list
+    a0,a1,a2,a3 = ast
+    case a0
+    when :def!
+        return env.set(a1, EVAL(a2, env))
+    when :"let*"
+        let_env = Env.new(env)
+        a1.each_slice(2) do |a,e|
+            let_env.set(a, EVAL(e, let_env))
+        end
+        return EVAL(a2, let_env)
+    when :do
+        eval_ast(ast[1..-2], env)
+        ast = ast.last
+    when :if
+        cond = EVAL(a1, env)
+        if not cond
+            return nil if a3 == nil
+            ast = a3
+        else
+            ast = a2
+        end
+    when :"fn*"
+        return Function.new(a2, env, a1) {|*args|
+            EVAL(a2, Env.new(env, a1, args))
+        }
+    else
+        el = eval_ast(ast, env)
+        f = el[0]
+        if f.class == Function
+            ast = f.ast
+            env = f.gen_env(el.drop(1))
+        else
+            return f[*el.drop(1)]
+        end
+    end
+
+    end
+end
+
+# print
+def PRINT(exp)
+    return _pr_str(exp, true)
+end
+
+# repl
+repl_env = Env.new
+RE = lambda {|str| EVAL(READ(str), repl_env) }
+REP = lambda {|str| PRINT(EVAL(READ(str), repl_env)) }
+_ref = lambda {|k,v| repl_env.set(k, v) }
+
+# Import core functions
+$core_ns.each &_ref
+
+# Defined using the language itself
+RE["(def! not (fn* (a) (if a false true)))"]
+
+while line = Readline.readline("user> ", true)
+    begin
+        puts REP[line]
+    rescue Exception => e
+        puts "Error: #{e}" 
+        puts "\t#{e.backtrace.join("\n\t")}"
+    end
+end
diff --git a/ruby/types.rb b/ruby/types.rb
index 02ca7a6..16d8d1e 100644
--- a/ruby/types.rb
+++ b/ruby/types.rb
@@ -1,6 +1,24 @@
+require "env"
+
 class List < Array
 end
 
 class Vector < Array
 end
 
+class Function < Proc
+    attr_accessor :ast
+    attr_accessor :env
+    attr_accessor :params
+
+    def initialize(ast=nil, env=nil, params=nil, &block)
+        super()
+        @ast = ast
+        @env = env
+        @params = params
+    end
+
+    def gen_env(args)
+        return Env.new(@env, @params, args)
+    end
+end