[heisig]

Connection Machine Lisp never made it into production, but this paper had a profound impact on my scientific career. In particular, it was the following comment in the paper that triggered me to develop the Petalisp programming language (https://github.com/marcoheisig/Petalisp):

> Nevertheless, we have implemented (on a single-processor system, the Symbolics 3600) an experimental version of Connection Machine Lisp with lazy xappings and have found it tremendously complicated to implement but useful in practice.

I think there is a moral here: Don't hesitate to experiment with crazy ideas (lazy xappings), and don't be afraid to openly talk about those experiments.

After eight years of development, I can definitely confirm that lazy arrays/xappings are tremendously complicated to implement but useful in practice :)

[pjmlp]

For me, it was the papers that made me realise how we could have a world were programming could abstract the underlying architecture, while still taking advantage of it being heterogeneous.

Something that only recently is starting to take shape in compute landscape.

Petalisp looks cool.

[abrax3141]

Not sure what you consider "production", but I used *Lisp extensively on the CM2 at Xerox PARC in the late 1980s. In fact, I published several papers based on this research.

[convolvatron]

i'm assuming you mean 'lazy' in the context of the paper and not more a general system of lazy evaluation. what was in particular that you found difficult about binding pure functions under the notion of a xapping? thanks so much for posting your work

[heisig]

Implementing lazy arrays or xappings naively is easy - the Petalisp reference backend has just 94 lines of code [1]. The challenge is to implement them efficiently. With eager evaluation, the programmer describes more or less precisely what the computer should do. With lazy evaluation, you only get a description of what should be done, with almost no no restriction on how to do it. To make lazy evaluation of arrays as fast as eager evaluation, you have to automate many of the high-level reasoning steps of an expert programmer. Doing so is extremely tedious, but once you have it you can write really clean and simple programs and still get the performance of hand-crafted wizard codes.

[1] https://github.com/marcoheisig/Petalisp/blob/master/code/cor...