mal/ruby/stepA_more.rb

require "readline"
require "types"
require "reader"
require "printer"
require "env"
require "core"

# read
def READ(str)
    return read_str(str)
end

# eval
def is_pair(x)
    return sequential?(x) && x.size > 0
end

def quasiquote(ast)
    if not is_pair(ast)
        return List.new([:quote, ast])
    elsif ast[0] == :unquote
        return ast[1]
    elsif is_pair(ast[0]) && ast[0][0] == :"splice-unquote"
        #p "xxx:", ast, List.new([:concat, ast[0][1], quasiquote(ast.drop(1))])
        return List.new([:concat, ast[0][1], quasiquote(ast.drop(1))])
    else
        return List.new([:cons, quasiquote(ast[0]), quasiquote(ast.drop(1))])
    end
end

def macro_call?(ast, env)
    return (ast.is_a?(List) &&
            ast[0].is_a?(Symbol) &&
            env.find(ast[0]) &&
            env.get(ast[0]).is_a?(Function) &&
            env.get(ast[0]).is_macro)
end

def macroexpand(ast, env)
    while macro_call?(ast, env)
        mac = env.get(ast[0])
        ast = mac[*ast.drop(1)]
    end
    return ast
end

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

    #puts "EVAL: #{_pr_str(ast, true)}"

    if not ast.is_a? List
        return eval_ast(ast, env)
    end

    # apply list
    ast = macroexpand(ast, env)
    return ast if not ast.is_a? 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 :quote
        return a1
    when :quasiquote
        return EVAL(quasiquote(a1), env)
    when :defmacro!
        func = EVAL(a2, env)
        func.is_macro = true
        return env.set(a1, func)
    when :macroexpand
        return macroexpand(a1, env)
    when :"rb*"
        return eval(a1)
    when :"try*"
        begin
            return EVAL(a1, env)
        rescue Exception => exc
            if exc.is_a? MalException
                exc = exc.data
            else
                exc = exc.message
            end
            if a2 && a2[0] == :"catch*"
                return EVAL(a2[2], Env.new(env, [a2[1]], [exc]))
            else
                raise esc
            end
        end
    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

_ref[:"readline", lambda {|prompt| Readline.readline(prompt,true)}]
_ref[:"read-string", lambda {|str| read_str str}]
_ref[:eval, lambda {|ast| EVAL(ast, repl_env)}]
_ref[:slurp, lambda {|f| File.read(f) }]

# Defined using the language itself
RE["(def! not (fn* (a) (if a false true)))"]
RE["(defmacro! cond (fn* (& xs) (if (> (count xs) 0) (list 'if (first xs) (if (> (count xs) 1) (nth xs 1) (throw \"odd number of forms to cond\")) (cons 'cond (rest (rest xs)))))))"]
RE["(defmacro! or (fn* (& xs) (if (empty? xs) nil (if (= 1 (count xs)) (first xs) `(let* (or_FIXME ~(first xs)) (if or_FIXME or_FIXME (or ~@(rest xs))))))))"]

RE["(def! load-file (fn* (f) (eval (read-string (str \"(do \" (slurp f) \")\")))))"]

p Dir.pwd
if ARGV.size > 0
    ARGV.each {|f|
        RE["(load-file \"" + f + "\")"]
    }
    exit 0
end
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