From: Jorgen Sigvardsson
Subject: How to parse strings into floats?
Date:
Message-ID: <3389DEE8.F01@wermland.se>
Hi.
I'm a student of Computer Science that just have begun learning LISP.
As I'm learning the language on my own (My University does not offer
LISP-courses), I have stumbled into a little problem. How does one parse
strings into floats? There is a parse-integer function but no equivalent
for floats. Is there an easy way to do this or do I have to do it the
hard way?
Thanks!
// Jorgen
From: William Paul Vrotney
Subject: Re: How to parse strings into floats?
Date:
Message-ID: <vrotneyEAt7Cw.9w1@netcom.com>
In article <············@wermland.se> Jorgen Sigvardsson
<······@wermland.se> writes:
>
> I'm a student of Computer Science that just have begun learning LISP.
> As I'm learning the language on my own (My University does not offer
> LISP-courses),
Sometimes Lisp is taught as an adjunct to an introductory AI course.
> I have stumbled into a little problem. How does one parse
> strings into floats? There is a parse-integer function but no equivalent
> for floats. Is there an easy way to do this or do I have to do it the
> hard way?
>
> Thanks!
>
> // Jorgen
What Lisp are you using? If you have Common Lisp just use READ-FROM-STRING
(setq /a (read-from-string "2.7"))
2.7
(describe /a)
2.7 is a SINGLE-FLOAT
--
William P. Vrotney - ·······@netcom.com
In article <·················@netcom.com> ·······@netcom.com (William Paul Vrotney) writes:
From: ·······@netcom.com (William Paul Vrotney)
Newsgroups: comp.lang.lisp
Date: Mon, 26 May 1997 22:19:44 GMT
Organization: Netcom On-Line Services
References: <············@wermland.se>
Lines: 31
Sender: ·······@netcom15.netcom.com
In article <············@wermland.se> Jorgen Sigvardsson
<······@wermland.se> writes:
>
> I'm a student of Computer Science that just have begun learning LISP.
> As I'm learning the language on my own (My University does not offer
> LISP-courses),
Sometimes Lisp is taught as an adjunct to an introductory AI course.
> I have stumbled into a little problem. How does one parse
> strings into floats? There is a parse-integer function but no equivalent
> for floats. Is there an easy way to do this or do I have to do it the
> hard way?
>
> Thanks!
>
> // Jorgen
What Lisp are you using? If you have Common Lisp just use READ-FROM-STRING
(setq /a (read-from-string "2.7"))
2.7
(describe /a)
2.7 is a SINGLE-FLOAT
READ-FROM-STRING does not quite cut it in many occasions. However,
St. Mark Kantrowitz has a PARSE-FLOAT package sitting in the
AI.Repository
http://www.cs.cmu.edu/afs/cs.cmu.edu/project/ai-repository/ai/html/air.html
Cheers
--
Marco Antoniotti
==============================================================================
California Path Program - UCB
Richmond Field Station
tel. +1 - 510 - 231 9472
A paper by William D. Clinger in PLDI90 described an algorithm for reading
floating-point numbers accurately:
Proceedings of the ACM SIGPLAN'90 Conference on Programming
Language Design and Implementation (PLDI), White Plains, New York,
June 20-22, 1990. SIGPLAN Notices 25(6) (June 1990)
William D. Clinger: How to Read Floating-Point Numbers Accurately.
pp. 92-101
I'm still looking for a machine-readable version of this paper, or of the
code.
Greetings,
Jens.
--
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