ftp.cs.arizona.edu/ftp.cs.arizona.edu.tar/ftp.cs.arizona.edu/icon/newsgrp/group94a.txt/000178_icon-group-sender _Thu Jun 16 21:43:30 1994.msg

Internet Message Format | 1994-08-19 | 2KB

Received: by cheltenham.cs.arizona.edu; Fri, 17 Jun 1994 08:06:39 MST
Date: Thu, 16 Jun 1994 21:43:30 MST
From: "Clinton L. Jeffery" <cjeffery>
Message-Id: <[e-mail]>
To: [e-mail]
Cc: [e-mail]
In-Reply-To: Eric Armstrong's message of Thu, 16 Jun 94 12:27:04 PDT <[e-mail]>
Subject: Re: booleans, enumerations, globals
Status: R
Errors-To: [e-mail]

   [Eric writes:]
   I'm wondering what idioms you guys use to:

       a. Do a simple boolean test, like
           if a=true    -or-   if a=false

As in LISP, use of the null value is common for this sort of value.
        if \a then ... # if a is not null <==> if a is true
        if /a then ... # if a is null <==> if a is false
Note that most Icon-ers avoid "boolean variables" entirely when they can.

       b. Create something like a Pascal enumeration type
          Days of the week, for example.  I create a list of strings:
          ["Mon", "Tue", ...] but then I index it by a number (weekday[2]).
          How would it be possible to index it as weekday[Tue]?

Two options come to mind, both dependent upon recent additions to Icon.
I am not sure if they are both in 8.10; I think at least option #1 is.

Option #1 is to $define each value in your enumeration:
$define Mon 1
$define Tue 2

Option #2 is to define a record type
record week(Mon,Tue,Wed,Thu,Fri,Sat,Sun)

then if weekday := week() you can say weekday.Mon or weekday["Mon"]

       c. initialize globals

There is no help for this and it is a deficiency in the language.
How much is fixing it worth?  :-)

Clint Jeffery, [e-mail], [e-mail]
U. of Texas at San Antonio