Lambda the Ultimate

Niklaus Wirth. Good Ideas, Through the Looking Glass, IEEE Computer, Jan. 2006, pp. 56-68.

An entire potpourri of ideas is listed from the past decades of Computer Science and Computer Technology. Widely acclaimed at their time, many have lost in splendor and brilliance under today’s critical scrutiny. We try to find reasons. Some of the ideas are almost forgotten. But we believe that they are worth recalling, not the least because one must try to learn from the past, be it for the sake of progress, intellectual stimulation, or fun.

A personal look at some ideas, mostly from the field of programming languages. Some of Wirth's objections are amusing, some infuriating - and some I agree with...

LtU readers will obviously go directly to sections 4 (Programming Language Features) and 6 (Programming Paradigms). Here are a few choice quotes:

It has become fashionable to regard notation as a secondary issue depending purely on personal taste. This may partly be true; yet the choice of notation should not be considered an arbitrary matter. It has consequences, and it reveals the character of a language. [Wirth goes on to discuss = vs. == in C...]

Enough has been said and written about this non-feature [goto] to convince almost everyone that it is a primary example of a bad idea. The designer of Pascal retained the goto statement (as well as the if statement without closing end symbol). Apparently he lacked the courage to break with convention and made wrong concessions to traditionalists. But that was in 1968. By now, almost everybody has understood the problem, but apparently not the designers of the latest commercial programming languages, such as C#.

The concept that languages serve to communicate between humans had been completely blended out, as apparently everyone could now define his own language on the fly. The high hopes, however, were soon damped by the difficulties encountered when trying to specify, what these private constructions should mean. As a consequence, the intreaguing idea of extensible languages faded away rather quickly.

LtU readers are also going to "enjoy" what Wirth has to say about functional programming...

(Thanks Tristram)

Via the PLT Scheme mailing list:

MzScheme's support for prompts and composable continuations most
closely resembles Dorai Sitaram's tagged `%' and `fcontrol' operators;
see "Handling Control", PLDI'93 [previously mentioned at LtU], or see Dorai's dissertation.

You can read about the primitive functionality of delimited continuations in the language manual. You can read about all the different control operators available in the new control.ss library in library manual. Among them: %, fcontrol, prompt, control, prompt-at, control-at, reset, shift, reset-at, shift-at, prompt0, reset0, control0, shift0, prompt0-at, reset0-at, control0-at, shift0-at, set, cupto.

(To prevent any confusion: this change is in the latest SVN but not yet a final release.)