simonbrooke

Objections:

1. the Xerox Lisp machines all used highly configurable processors which ran Lisp microcode, right back from the Alto; and by the time they got to the 1186 Daybreak it was a single chip, so a microprocessor. So to say they didn't have a Lisp microprocessor is sort of a misunderstanding. Although it's fair to say that memory was limited, and that performance was not on a par with the Symbolics or TI machines.

2. Common Lisp was very different from Interlisp, but that wasn't driven by customers.

It's worth reading Gabriel and Steele's 'The Evolution of Lisp'; neither author can be described as an Interlisp advocate, although the paper is reasonably fair. Full disclosure, I played a minor part in the European Lisp standardisation committees (under ISO WG 16) in the mid eighties, so I'm not an unbiased observer either. The conflict between European and US groups is documented (from a US perspective) in section 2.12.11 of the paper.

But essentially, I think I can say uncontroversially, the ascent of Common Lisp was highly political, and most certainly not customer driven.

Larry Massinter (et al)'s work to get Interlisp going on stock hardware is indeed a very welcome thing, but we've lost thirty years of evolution and development. Until it can address the host operating system's windowing layer, rather than running in a single window, it will remain a curiosity.

There certainly was a lot of mystique about Genera; I only got to play with a Symbolics machine once. But, although it was the very top end of the US East Coast Lisp machines, it was just a US East Coast Lisp machine. You edited files, you did not edit in core. You edited with a text editor, you did not edit with a structure editor. You did not have the vast range of graphical code inspection and exploration tools that we had on Interlisp (or if you did they didn't show them off), and the break inspector was just as crude and clunky as it is on a modern Common Lisp system.

My understanding is that the Symbolics machines were a lot faster than our Dandelions and Daybreaks (I never got to play with a Dorado, either...), but... I honestly don't believe they were in the same class.

Mind you, the other Lisp machine of that era that I really lusted after, the Connection Machine, I never got to play with at all, although there was one being used for something very hush-hush and defence related in one of the labs some of our machines were in.

Interlisp was about fifty years ahead of modern software development systems; Genera was forty years behind (which is fair enough, it was forty years ago).

It hasn't happened to me. I started coding in 1982; I'm still doing it. In the meantime I've started four startups (none of which succeeded - I'm a much better geek than I am a businessman - and done a couple of management jobs. But I find I still prefer writing code (and designing systems) to anything else, and I don't at all enjoy being responsible for seeing that there's enough money in the bank to pay other people's wages, so these days I'm just a contract programmer.

This is a beautiful essay, and I've really enjoyed it. However, while interesting and inspirational it doesn't all ring true. Lisps from the years before generational garbage collection might spend five percent of their time in GC; in particularly awkward cases it might rise to ten percent. I'm not saying this was desirable: it was not, particularly in interactive processes. But it was nothing like 'usually spent between a third and half of their time running the garbage collector'.

I've seen some very long GCs indeed. I'm sure I've seen fifteen minute GCs. But I've never seen GC eat a third of the processor cycles. I don't believe it.