paiza.ioでelixir その48

概要

paiza.ioでelixirやってみた。
練習問題やってみた。

練習問題

Forthインタープリタを書け。
forthで数9を4個つかって1から15までの数を表す式を実行せよ。
Tupleを使え。

サンプルコード

defmodule Forth do
	def start_link do
		Agent.start_link(fn ->
			{}
		end, name: __MODULE__)
	end
	def add do
		Agent.update(__MODULE__, fn stack ->
		    po = tuple_size(stack) - 1
		    top = elem(stack, po)
		    nd = elem(stack, po - 1)
		    stack = put_elem(stack, po - 1, nd + top)
		    stack = Tuple.delete_at(stack, po)
		end)
	end
	def sub do
		Agent.update(__MODULE__, fn stack ->
		    po = tuple_size(stack) - 1
		    top = elem(stack, po)
		    nd = elem(stack, po - 1)
		    stack = put_elem(stack, po - 1, nd - top)
		    stack = Tuple.delete_at(stack, po)
		end)
	end
	def mul do
		Agent.update(__MODULE__, fn stack ->
		    po = tuple_size(stack) - 1
		    top = elem(stack, po)
		    nd = elem(stack, po - 1)
		    stack = put_elem(stack, po - 1, nd * top)
		    stack = Tuple.delete_at(stack, po)
		end)
	end
	def div do
		Agent.update(__MODULE__, fn stack ->
		    po = tuple_size(stack) - 1
		    top = elem(stack, po)
		    nd = elem(stack, po - 1)
		    stack = put_elem(stack, po - 1, nd / top)
		    stack = Tuple.delete_at(stack, po)
		end)
	end
	def dup do
		Agent.update(__MODULE__, fn stack ->
		    po = tuple_size(stack) - 1
			top = elem(stack, po)
			stack = Tuple.append(stack, top)
		end)
	end
	def drop do
		Agent.update(__MODULE__, fn stack ->
		    po = tuple_size(stack) - 1
			stack = Tuple.delete_at(stack, po)
		end)
	end
	def get do
		Agent.get(__MODULE__, fn stack ->
		    po = tuple_size(stack) - 1
			elem(stack, po)
		end)
	end
	def push(n) do
		Agent.update(__MODULE__, fn stack ->
		    {v, _} = Integer.parse(n)
			stack = Tuple.append(stack, v)
		end)
	end
end

defmodule Main do
    def run(str) do
    Enum.map(String.split(str, " "), fn s ->
        cond do
	    s == "+" ->
		    Forth.add
	    s == "-" ->
		    Forth.sub
	    s == "*" ->
		    Forth.mul
	    s == "/" ->
		    Forth.div
	    s == "dup" ->
		    Forth.dup
	    s == "drop" ->
		    Forth.drop
	    s == "." ->
		    IO.inspect Forth.get
	    true ->
            Forth.push(s)
        end
    end)
    end
end

Forth.start_link

Main.run("9 9 - 9 9 / .")

Main.run("9 9 / 9 9 / + .")# 2  ok

Main.run("9 9 + 9 + 9 / .")# 3  ok

Main.run("9 9 9 + 9 / dup + .")# 4  ok

Main.run("9 9 9 + 9 / dup + - .")# 5  ok

Main.run("9 dup 9 + 9 + 9 / - .")# 6  ok

Main.run("9 9 9 + 9 / - .")# 7  ok

Main.run("9 9 9 drop 9 / - .")# 8  ok

Main.run("9 9 - 9 * 9 + .")# 9  ok

Main.run("9 9 / 9 dup 9 / + .")# 10  ok

Main.run("9 9 9 + 9 / + .")# 11  ok

Main.run("9 dup 9 9 + + 9 / + .")# 12  ok

Main.run("9 9 9 + 9 / dup + + .")# 13  ok

Main.run("9 dup 9 9 + 9 / dup + - + .")# 14  ok

Main.run("9 dup dup 9 + 9 + 9 / - + .")# 15  ok

実行結果

1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9
10.0
11.0
12.0
13.0
14.0
15.0

成果物

以上。