Mike Schaeffer's Weblog
Wed, 16 Nov 2005
UseHR, I give up!!!
A few months ago I wrote a bit on the impact of high resolution displays on the way Internet Explorer renders graphics. I had really planned on using the default setting. Not anymore!

This is the awful default:


This is as it should be:


Now, guess what Firefox does.

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[/tech/general] permanent link

Wed, 09 Nov 2005
Thirty days hath September...

"Thirty days hath September,
All the rest I can't remember.
The calendar hangs on the wall;
Why bother me with this at all?"

http://leapyearday.com/30Days.htm



Here's an Excel one liner that computes the number of days in a particular month. Cell A2 contains the year of the month you're looking for, Cell B2 contains the months' ordinal (1=January, 2=February, etc.):
=DAY(DATE(A2,B2+1,1)-1)
This is mainly useful to illustrate what can be done with Excel's internal representation of dates. Dates and times in Windows versions of Excel are normally stored as the number of days from January 1st, 1900. You can see this by entering a date in a cell, and then reformatting the cell to display as a number rather than a date. For example, this reveals April 1st, 2004 to be represented internally as the number 38078. This is because there are 38,078 days between January 1st, 1900 and April 1st, 2004.

The formula above relies on this in its computation of the number of days in a month. The sub-expression DATE(A2,B2+1,1) computes the date number for the first day of the month immediately following the month we're interested in. We then subtract one from that number, which gives us the date number for the last day of the month that we are interested in. The call to DAY then returns the number of the day within the month, which happens to be the number of days in the month.

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Fri, 04 Nov 2005
SRFI-74: Octet-Addressed Binary Blocks
Michael Sperver has written an SRFI that documents "Octet-Addressed Binary Blocks". Basically these things are like BLOBs in SQL: blocks of memory, opaque to the data model of the language, that can be used to store arbitrary binary data. I can think of a bunch of applications for this:
  • An internal representation for compiled byte code functions.
  • A way to interoperate with C code that expects binary data formats. (Like the Win32 API, for example. )
  • A way to represent binary data longer than a byte that's written to and read from binary ports.


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[/tech/lisp] permanent link

Tips on Programming
I don't know who this person is, but they have a good collection of programming tips online. A lot of this stuff looks pretty relevant.

Related to that is this deck of slides written by Kent Pitman and Peter Norvig. It's an excellent discussion of good programming style in Lisp.

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"Apropos of..." Better Autofilter Results.
At my job, we use Excel extensively to keep track of software testing progress. One typical use is to maintain a list of features to be tested, along with their current pass/fail statuses and an attempt at a rough subdivision into functional areas. Excel's AutoFilter then makes it easy to ask questions like "show me all failed tests relating to function block scheduling."

This works really well as long as "function block scheduling" is one of the categories into which you've subdivided your features list. If it's not, you have to get a little creative to filter your list. One approach to this problem I've found useful is filtering based on columns populated with a formula similar to this:
=IF(ISERROR(SEARCH($K$5,K6)),"No","Yes")
If column K contains feature descriptions, this formula returns "Yes" is the description matches the search string in K5 and "No", otherwise. Filtering based on this formula makes it possible to display every list item whose description matches a word. If there is more than one column to search, you can use string concatenation to aggregate the columns together:
=IF(ISERROR(SEARCH($K$5,K6&L6&M6)),"No","Yes")
So, why the name apropos? Follow this link.

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