Scheme - 積極制御評価器(新しい基本的特殊形式としてcondを実装)

計算機プログラムの構造と解釈
Gerald Jay Sussman, Julie Sussman
Harold Abelson (原著) 和田 英一 (翻訳)

開発環境

• OS X Mavericks - Apple(OS)
• Emacs (CUI)、BBEdit - Bare Bones Software, Inc. (GUI) (Text Editor)
• Scheme (プログラミング言語)
• MIT/GNU Scheme (処理系)

計算機プログラムの構造と解釈(Gerald Jay Sussman(原著)、Julie Sussman(原著)、Harold Abelson(原著)、和田 英一(翻訳)、ピアソンエデュケーション、原書: Structure and Interpretation of Computer Programs (MIT Electrical Engineering and Computer Science)(SICP))の5(レジスタ計算機での計算)、5.4(積極制御評価器)、5.4.1(積極制御評価器の中核)、単純式の評価、手続き作用の評価、手続き作用、5.4.2(並びの評価と末尾再帰)、末尾再帰、5.4.3(条件式、代入および定義)、代入と定義、問題 5.24.を解いてみる。

その他参考書籍

• Instructor's Manual to Accompany Structure & Interpretation of Computer Programs

問題 5.24.

追加箇所。

eval-dispatch
  (test (op self-evaluating?) (reg exp))
  (branch (label ev-self-eval))
  (test (op variable?) (reg exp))
  (branch (label ev-variable))
  (test (op quoted?) (reg exp))
  (branch (label ev-quoted))
  (test (op assignment?) (reg exp))
  (branch (label ev-assignment))
  (test (op definition?) (reg exp))
  (branch (label ev-definition))
  (test (op if?) (reg exp))
  (branch (label ev-if))
  (test (op lambda?) (reg exp))
  (branch (label ev-lambda))
  (test (op begin?) (reg exp))
  (branch (label ev-begin))
  (test (op cond?) (reg exp))
  (branch (label ev-cond))
  (test (op let?) (reg exp))
  (branch (label ev-let))
  (test (op application?) (reg exp))
  (branch (label ev-application))
  (goto (label unknown-expression-type))
;; …
ev-cond
  (assign unev (op cond-clauses) (reg exp))
  (save continue)
  (goto (label ev-cond-loop))
ev-cond-loop
  (test (op null?) (reg unev))
  (branch (label ev-cond-null))
  (assign exp (op car) (reg unev))
  (test (op cond-else-clause?) (reg exp))
  (branch (label ev-cond-else))
  (save exp)
  (assign exp (op cond-predicate) (reg exp))
  (save unev)
  (save env)
  (assign continue (label ev-cond-decide))
  (goto (label eval-dispatch))
ev-cond-null
  (restore continue)
  (assign val (const #f))
  (goto (reg continue))
ev-cond-else
  (assign unev (op cond-actions) (reg exp))
  (goto (label ev-sequence))
ev-cond-decide
  (restore env)
  (restore unev)
  (restore exp)
  (test (op true?) (reg val))
  (branch (label ev-cond-consequent))
  (assign unev (op cdr) (reg unev))
  (goto (label ev-cond-loop))
ev-cond-consequent
  (assign unev (op cond-actions) (reg exp))
  (goto (label ev-sequence))

まだ積極制御評価器の実装し終わってないから、実装したら入出力も試してみることに。