[jawsscripts] Re: One of my wilder debugging discoveries
- From: "Geoff Chapman" <gch@xxxxxxxxxxxxxxxx>
- To: <jawsscripts@xxxxxxxxxxxxx>
- Date: Fri, 22 Nov 2013 11:59:19 +1100
Yeah Doug your a veritable gem of information when it comes to those off the
beaten track discoveries in this world. Thanks for sharing indeed!
----- Original Message -----
From: "Chad Foster" <chad.foster@xxxxxxxxxx>
To: <jawsscripts@xxxxxxxxxxxxx>; "Doug Lee" <doug.lee@xxxxxxxxxxxxxxxx>
Sent: Friday, November 22, 2013 4:49 AM
Subject: [jawsscripts] Re: One of my wilder debugging discoveries
> Thanks for sharing Doug. it's always helpful to learn a few more
> potential potholes and how to guard against them.
>
> On 11/21/13, Doug Lee <doug.lee@xxxxxxxxxxxxxxxx> wrote:
>> This just seems worth writing down for its oddity...
>>
>> I was debugging a 23,000-line script this morning. Recently I started
>> getting really strange behavior when trying to assign collections to
>> variables in part of the code: I started getting the integer 1 in
>> place of a collection, with no obvious reason. I tried myriad
>> solutions and debugging tricks, sayString/sayInteger lines, etc.
>>
>> Then I added a sayInteger at a particular point in the code, and presto,
>> the thing started working! "How strange," I thought, "that shouldn't
>> affect anything, it's not making an assignment..."
>>
>> So I took the new line out, and the odd wrong behavior resumed.
>>
>> On reading more carefully, I found that the next line after the
>> sayInteger I had put in began with a spurious less-than sign (<).
>> Apparently I had mistakenly copied that line out of a diff output
>> file, in which less-than signs indicate removed lines and greater-than
>> signs indicate added ones.
>>
>> I should mention here two things: I read with punctuation off, and in
>> my actual code files, which are sometimes something like templates, I
>> use a double less-than to indicate a translatable symbol; so I am
>> accustomed to ignoreing less-than signs as I read anyway.
>>
>> The previous line in the file was an assignment like
>>
>> cLocation = locations[index]
>>
>> in other words, an assignment from an array to a collection variable. The
>> line after that was a plain old function call, we'll say MyFunc(). So
>> the code before my sayInteger was added looked like
>>
>> cLocation = locations[index]
>> < myFunc()
>>
>> The JAWS script compiler treats end-of-line no different than a space
>> most of the time, so it read the above two lines like
>>
>> cLocation = locations[index] < myFunc()
>>
>> which actually means, assign to cLocations the integer (boolean) value
>> of the question, is locations[index] less than the return value of
>> myFunc()?
>>
>> It so happens that myFunc() returns True, which as an integer is
>> 1. I guess the integer value of the collection at locations[index]
>> was 0, so the above question's result was True, which is also a 1
>> when taken as an integer. This is how cLocation was getting set
>> to 1 instead of a collection.
>>
>> Now, when I put the sayInteger call in, why did I get a different
>> result? The code would then look like
>>
>> cLocation = locations[index]
>> sayInteger(...)
>> < myFunc()
>>
>> Now the spurious less-than sign doesn't affect the assignment. JAWS
>> will actually make the comparison
>>
>> sayInteger(...) < myFunc()
>>
>> but then discard it because it's not being assigned to anything.
>> This had the net effect of making my cLocation assignment work
>> again.
>>
>> And they wonder why it is said we'll spend 90% of our time debugging.
>> :-)
>>
>>
>>
>> --
>> Doug Lee, Senior Accessibility Programmer
>> SSB BART Group - Accessibility-on-Demand
>> mailto:doug.lee@xxxxxxxxxxxxxxxx http://www.ssbbartgroup.com
>> "While they were saying among themselves it cannot be done,
>> it was done." --Helen Keller
>> __________�
>>
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>>
>>
>
>
> --
> Chad Foster
> Access Technology Solutions
> Leveling The Playing Field Through Technology
> http://www.GO-ATS.net
> __________�
>
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