Using PLY, write an interpreter for the language of "LISP expressions". A LISP expression is defined as follows: A number (integer as well as fractional) is a LISP expression. if E1 and E2 are LISP expressions then so are (+ E1 E2), (- E1 E2), (* E1 E2), and (/ E1 E2). if L is a LIST expression (defined below) then (car L) is a LISP expression. if B is a BOOLEAN expression and E1 and E2 are LISP expressions then (if B E1 E2) is a LISP expression. A LIST Expression is defined as follows: if E1, E2, ..., En are LISP expressions where n>=0 then (E1 E2 ... En) is a LIST expression. if L is a LIST expression then (cdr L) is a LIST expression. if E is a LISP expression and L is a LIST expression then (cons E L) is a LIST expression. A BOOLEAN expression is defined as follows: True and False are BOOLEAN expressions. if E1 and E2 are LISP expressions then (> E1 E2), (>= E1 E2), (< E1 E2), (<= E1 E2), (= E1 E2), and (<> E1 E2) are BOOLEAN expressions. if B1 and B2 are BOOLEAN expressions then so are (not B1), (and B1 B2), and (or B1 B2). Here are examples of valid LISP expressions:34 True (20 30 40) (+ 20 30) (* (+ 1 2) (/ 8 4)) (* (car (2 4 (+ 2 4) 8)) (/ 27 9)) (+ (car (2 3 4)) (car (cdr (cdr (9 8 7 6))))) (if (> 2 3) 40 50) (and (> 2 3) (> 3 2)) (cdr (cons (+ 2 3) (4 5 6))) Here is a sample run:Mac-mini:hw1 raj$ python3 LISP.py LISP: 34; 34.0 LISP: (+ 20 30); 50.0 LISP: (/ 9 (- 2 2)); DIVIDE BY ZERO! LISP: (* (+ 1 2) (/ 8 4)); 6.0 LISP: (* (car (2 4 (+ 2 4) 8)) (/ 27 9)); 6.0 LISP: (+ (car (2 3 4)) (car (cdr (cdr (9 8 7 6))))); 9.0 LISP: (+ 2 3 4); Syntax error in input! LISP: (* (car 4) 22); Syntax error in input! LISP: (+ 3 (car (cdr (cdr (cdr (1 2)))))); Cannot CDR on an empty list! LISP: (if (> 2 3) 40 50); 50.0 LISP: (or (> 2 3) (> 3 2)); True LISP: (and (> 2 3) (> 3 2)); False LISP: (cdr (1 2 3 4)); (2.0 3.0 4.0) LISP: (cdr (cons (+ 2 3) (4 5 6))); (4.0 5.0 6.0) LISP: (cdr (cdr (1 2 3 4))); (3.0 4.0) LISP: (cdr (cdr (3 4))); () LISP: (cdr (cdr (3))); Cannot CDR on an empty list! LISP: (car (cdr (1 2 3 4))); 2.0 LISP: exit; Mac-mini:hw1 raj$ WHAT TO SUBMIT? LISP.py, LISPLexer.py, LISPParser.py. If you chose to implement the expression tree using LISPNode, then you must submit LISPNode.py as well.

Using PLY, write an interpreter for the language of "LISP expressions". A LISP expression is defined as follows: A number (integer as well as fractional) is a LISP expression. if E1 and E2 are LISP expressions then so are (+ E1 E2), (- E1 E2), (* E1 E2), and (/ E1 E2). if L is a LIST expression (defined below) then (car L) is a LISP expression. if B is a BOOLEAN expression and E1 and E2 are LISP expressions then (if B E1 E2) is a LISP expression. A LIST Expression is defined as follows: if E1, E2, ..., En are LISP expressions where n>=0 then (E1 E2 ... En) is a LIST expression. if L is a LIST expression then (cdr L) is a LIST expression. if E is a LISP expression and L is a LIST expression then (cons E L) is a LIST expression. A BOOLEAN expression is defined as follows: True and False are BOOLEAN expressions. if E1 and E2 are LISP expressions then (> E1 E2), (>= E1 E2), (< E1 E2), (<= E1 E2), (= E1 E2), and (<> E1 E2) are BOOLEAN expressions. if B1 and B2 are BOOLEAN expressions then so are (not B1), (and B1 B2), and (or B1 B2). Here are examples of valid LISP expressions:34 True (20 30 40) (+ 20 30) (* (+ 1 2) (/ 8 4)) (* (car (2 4 (+ 2 4) 8)) (/ 27 9)) (+ (car (2 3 4)) (car (cdr (cdr (9 8 7 6))))) (if (> 2 3) 40 50) (and (> 2 3) (> 3 2)) (cdr (cons (+ 2 3) (4 5 6))) Here is a sample run:Mac-mini:hw1 raj$ python3 LISP.py LISP: 34; 34.0 LISP: (+ 20 30); 50.0 LISP: (/ 9 (- 2 2)); DIVIDE BY ZERO! LISP: (* (+ 1 2) (/ 8 4)); 6.0 LISP: (* (car (2 4 (+ 2 4) 8)) (/ 27 9)); 6.0 LISP: (+ (car (2 3 4)) (car (cdr (cdr (9 8 7 6))))); 9.0 LISP: (+ 2 3 4); Syntax error in input! LISP: (* (car 4) 22); Syntax error in input! LISP: (+ 3 (car (cdr (cdr (cdr (1 2)))))); Cannot CDR on an empty list! LISP: (if (> 2 3) 40 50); 50.0 LISP: (or (> 2 3) (> 3 2)); True LISP: (and (> 2 3) (> 3 2)); False LISP: (cdr (1 2 3 4)); (2.0 3.0 4.0) LISP: (cdr (cons (+ 2 3) (4 5 6))); (4.0 5.0 6.0) LISP: (cdr (cdr (1 2 3 4))); (3.0 4.0) LISP: (cdr (cdr (3 4))); () LISP: (cdr (cdr (3))); Cannot CDR on an empty list! LISP: (car (cdr (1 2 3 4))); 2.0 LISP: exit; Mac-mini:hw1 raj$ WHAT TO SUBMIT? LISP.py, LISPLexer.py, LISPParser.py. If you chose to implement the expression tree using LISPNode, then you must submit LISPNode.py as well.

Database System Concepts

7th Edition

ISBN:9780078022159

Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Chapter1: Introduction

Section: Chapter Questions

Problem 1PE

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Question

Using PLY, write an interpreter for the language of "LISP expressions".

A LISP expression is defined as follows:

A number (integer as well as fractional) is a LISP expression.
if E1 and E2 are LISP expressions then so are (+ E1 E2), (- E1 E2), (* E1 E2), and (/ E1 E2).
if L is a LIST expression (defined below) then (car L) is a LISP expression.
if B is a BOOLEAN expression and E1 and E2 are LISP expressions then (if B E1 E2) is a LISP expression.

A LIST Expression is defined as follows:

if E1, E2, ..., En are LISP expressions where n>=0 then (E1 E2 ... En) is a LIST expression.
if L is a LIST expression then (cdr L) is a LIST expression.
if E is a LISP expression and L is a LIST expression then (cons E L) is a LIST expression.

A BOOLEAN expression is defined as follows:

True and False are BOOLEAN expressions.
if E1 and E2 are LISP expressions then (> E1 E2), (>= E1 E2), (< E1 E2), (<= E1 E2), (= E1 E2), and (<> E1 E2) are BOOLEAN expressions.
if B1 and B2 are BOOLEAN expressions then so are (not B1), (and B1 B2), and (or B1 B2).

Here are examples of valid LISP expressions:34 True (20 30 40) (+ 20 30) (* (+ 1 2) (/ 8 4)) (* (car (2 4 (+ 2 4) 8)) (/ 27 9)) (+ (car (2 3 4)) (car (cdr (cdr (9 8 7 6))))) (if (> 2 3) 40 50) (and (> 2 3) (> 3 2)) (cdr (cons (+ 2 3) (4 5 6))) Here is a sample run:Mac-mini:hw1 raj$ python3 LISP.py LISP: 34; 34.0 LISP: (+ 20 30); 50.0 LISP: (/ 9 (- 2 2)); DIVIDE BY ZERO! LISP: (* (+ 1 2) (/ 8 4)); 6.0 LISP: (* (car (2 4 (+ 2 4) 8)) (/ 27 9)); 6.0 LISP: (+ (car (2 3 4)) (car (cdr (cdr (9 8 7 6))))); 9.0 LISP: (+ 2 3 4); Syntax error in input! LISP: (* (car 4) 22); Syntax error in input! LISP: (+ 3 (car (cdr (cdr (cdr (1 2)))))); Cannot CDR on an empty list! LISP: (if (> 2 3) 40 50); 50.0 LISP: (or (> 2 3) (> 3 2)); True LISP: (and (> 2 3) (> 3 2)); False LISP: (cdr (1 2 3 4)); (2.0 3.0 4.0) LISP: (cdr (cons (+ 2 3) (4 5 6))); (4.0 5.0 6.0) LISP: (cdr (cdr (1 2 3 4))); (3.0 4.0) LISP: (cdr (cdr (3 4))); () LISP: (cdr (cdr (3))); Cannot CDR on an empty list! LISP: (car (cdr (1 2 3 4))); 2.0 LISP: exit; Mac-mini:hw1 raj$

WHAT TO SUBMIT?

LISP.py, LISPLexer.py, LISPParser.py. If you chose to implement the expression tree using LISPNode, then you must submit LISPNode.py as well.

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