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Thursday, March 17, 2005

Call Scan() Routine

Here's a nice new SAS function/call routine thingy that I used recently:
call scan()

It works kinda like the scan() function, except it gives the index and length of the word. I was needing to look through text for a particular keyword and then I wanted to find other keywords within five words on either side. Say I'm looking for FIRE. And I want to know if HOUSE or CAR appears within five words. Before, I would have done this type of thing in PERL using it's sweet hash tables. But with call scan() I can get the position of a word, use substrn() to check for my keyword and then loop back and forth scan()ning for my other words.


Monday, March 07, 2005

Kicking The Macro Habit

I do a lot of work with SAS macro. I use it daily, but I must admit, I find the resulting code kludgy and ugly. Being able to write code that writes code is indeed powerful, but it comes with a cumbersome price: all those % signs, ampersands, the semi-colon that will sometimes get gobbled up by the compiler, local and global symbol tables, %sysfunc() to get to base functions, all those wacky quoting functions %NRBSTR( aaaarrrrrgggh! ), limited debugging, etc etc etc.

Plus, I have met many, many otherwise competent programmers that just can't seem to quite _get_ full scale macro programming. Like pointers to pointers in C, at some point the thread just unravels.

Now don't get my wrong. I think macro is a valuable skillset, and has a valuable place in your programming toolbox, but for large, complex applications I am always thinking there's got to be a better way.

SCL comes to mind. You can use it to write base sas code to the program stack just like macro, with the added benefit that you can manipulate and recall the stack. Imagine getting to recall all the base sas code that your big complicated macro produced instead of having to parse your log. There's other benefits too: built in data types arrays and lists; SCL debugging and compiling; much cleaner syntax, and clearly defined submit blocks; variable locality using declare, just to name a few.

So does anybody use SCL this way? I've been thinking about it for a while, but I haven't yet. Using SAS catalogs instead of text source files would be a drawback for me. Are there any other drawbacks?

Maybe those programmers that don't get large scale macro programming just have more attuned programming sensibilites than me. They see all those %'s and &'s and their refined programming brain wanders away in disgust. Maybe I will code my next large application in SCL from the beginning instead of turning to macro out of habit. But old habits are hard to break.