[plt-scheme] Re: hash-has-key?

From: Carl Eastlund (carl.eastlund at gmail.com)
Date: Fri Apr 17 12:47:10 EDT 2009

On Fri, Apr 17, 2009 at 9:18 AM, TPJ <tprimke at gmail.com> wrote:
> On 28 Mar, 01:14, Henk Boom <h... at henk.ca> wrote:
>> Hi, I was looking for a way to test whether or not a hash table has a
>> mapping for a given key. I was surprised not to find anything in the
>> docs (...)
> Interesting. I found hash-has-key? in the PLT Reference
> (http://docs.plt-scheme.org/reference/hashtables.html), but I cannot
> use it:
> Welcome to DrScheme, version 4.1.4 [3m].
> Language: Module; memory limit: 128 megabytes.
>> (define a (make-hash))
>> (hash-has-key? a 'key)
> . . reference to undefined identifier: hash-has-key?
> What's wrong? (I'm new to Scheme and to PLT Scheme.)


The online documentation refers to the latest development version of
PLT Scheme.  Note that the upper right hand corner of the page you
link to says "Version:", whereas the program you ran says
"version 4.1.4".

If you want documentation corresponding to your version of PLT Scheme,
open up the Help Desk from the Help menu of your application.  On the
other hand, if you want the latest version of PLT Scheme corresponding
to the online documentation, download it from:

Carl Eastlund

Posted on the users mailing list.