15 - INSTANCE-SPECIFIC BEHAVIOR: DIGITALK IMPLEMENTATION AND THE DEEPER MEANING OF IT ALL

Summary

Well, at least I didn't just present instance-specific behavior as a pointy-hat technique. I tried to extract some cultural lessons from it. Now that the Smalltalk world has contracted to a couple of big players, there isn't enough cultural diversity left to analyze. Ah, the olden days, back when we used to have to walk miles barefoot in the snow to get coal to shovel into our Smalltalk machines… Now I sound like an old fart

In the last issue, I wrote about what instance-specific behavior is, why you would choose to use it, and how you implement it in Smalltalk-80 …er…Objectworks\Smalltalk (which way does the slash go, anyhow?) …er… VisualWorks (is that a capital W or not?). This month's column offers the promised Digitalk Smalltalk/V OS/2 2.0 implementation (thanks to Mike Anderson for the behind-the-scenes info) and a brief discussion of what the implementations reveal about the two engineering organizations.

I say “brief discussion” because as I got to digging around I found many columns' worth of material there for the plucking. I'll cover only issues raised by the implementation of classes and method look-up. Future columns will contrast the styles as they apply to operating system access, user interface frameworks, and other topics.