4 ms·

William Byrd on ”The Most Beautiful Program Ever Written” (2017) [video]

43 points by lelf 8y ago

getpost 8y ago
...Namely, an interpreter for lisp written in lisp. William Byrd learned about it from Daniel P. Friedman (The Little Lisper, The Little Schemer, ....)
keithnz 8y ago
Alan Kay said :- (SF) If nothing else, Lisp was carefully defined in terms of Lisp. (AK) Yes, that was the big revelation to me when I was in graduate school—when I finally understood that the half page of code on the bottom of page 13 of the Lisp 1.5 manual was Lisp in itself. These were “Maxwell’s Equations of Software!” This is the whole world of programming in a few lines that I can put my hand over. https://queue.acm.org/detail.cfm?id=1039523 https://queue.acm.org/detail.cfm?id=1039523
- WalterGR 8y ago
  Preformatted text on HN is really hard to read on mobile. Reformatted: (SF) If nothing else, Lisp was carefully defined in terms of Lisp. (AK) Yes, that was the big revelation to me when I was in graduate school—when I finally understood that the half page of code on the bottom of page 13 of the Lisp 1.5 manual was Lisp in itself. These were “Maxwell’s Equations of Software!” This is the whole world of programming in a few lines that I can put my hand over. Page 13 of that manual is page 21 of this PDF: http://www.softwarepreservation.org/projects/LISP/book/LISP%201.5%20Programmers%20Manual.pdf http://www.softwarepreservation.org/projects/LISP/book/LISP%...
- ngcc_hk 8y ago
  Hard to read when quote like this.
kazinator 8y ago
Lisp in Lisp interpreters actually have a marginal practical use. Suppose you've boostrapped a Lisp in some other language (assembly, C or whatever). You have an interpreter in that language, and have written a compiler for that Lisp in itself (say for a VM in that other language). You can now write an interpreter for that Lisp in itself. Once that interpreter behaves exactly like the original one in the other language, you can throw that one away. Bootstrapping can proceed by shipping the interpreter in compiled form. The benefit is that there is less language-processing code written in the other language. You could just throw the interpreter away and have a compiler only (bootstrapped with the compiled version of itself), but then it's useful to have two models of execution for programs.
- bitwize 8y ago
  This is how we got the first working Lisp implementations. John McCarthy specified Lisp in itself, and a graduate student translated it into IBM 704 assembly.
ncmncm 8y ago
At great risk of being downvoted to oblivion (before you pile on, check your motives), this struck me on first encounter, 30 years ago, and ever more strongly since, as the most self-indulgent of all programs. People impressed by it invariably appear, primarily, pleased with themselves for the depth of perception they demonstrate by being impressed with it. Comparing it to Maxwell's equations sharpens this. The equations are deeply illuminative of fundametal processes of reality, summarizing comprehensively and precisely decades of exacting experimentation by the best physicists of the age. The speed of light (in vacuum, and in any medium) is simply derived from them. No detail of them could be deduced without abstraction from all the experience of all who came before. How much work went into this program? Would any two people, who just knew Lisp, but no theory of computation, asked to write it, write it differently? How long could it take? An hour, a week, a month? How much insight would it take? How much lived experience does it represent? Think it through: A Lisp interpreter in Lisp. It demonstrates that, if you are handed a Lisp runtime, as we are today, it is easy to make it execute Lisp programs. With small changes, it runs slightly different programs. Should that impress us? Where did this Lisp runtime come from, and why would one expect it to be tuned for anything but running Lisp programs? If it were not good for running Lisp programs, what would it be good for? The program relies, fundamentally, on all the science (and, frankly, engineering) that came before, but illuminates none of it. It is a fleck of foam that rides determinedly at the surface, belying the depths that support it. It illuminates nothing beyond itself.
- kazinator 8y ago
  > Where did this Lisp runtime come from, and why would one expect it to be tuned for anything but running Lisp programs? In this case, it's running a program which very itself easily runs Lisp programs given to it as a source code data structure. That we normally don't expect. For instance, in C language run-time, though it of course supports running compiled C programs, it doesn't provide a straightforward way for one of these programs to itself process C programs. A C program that interprets a decent subset of C is pretty complicated. It has to provide a number of data structures, of course a parser (because C programs don't have a data structural representation) and memory management for the parse time and run-time and so on. The C-processing C program can't even ask for a function by name so that it could resolve a function call out to the native run-time. This is possible with some operating system extensions (dynamic symbols). That just solves the name resolution problem: then there is the problem of dynamically constructing the argument list for a function call and executing it. This requires a library not supplied in the C language such as GNU ffcall, or libffi. Think about it: a C interpreter for C needs to use a FFI mechanism (first F == foreign!) to expose the C run time to the interpreted C, and that FFI is far from a standard language feature. Lisp just resolves a symbol and calls apply and that's it; nothing is foreign: no visas have to be issued, no passports are stamped.

43 points by lelf 8y ago

...Namely, an interpreter for lisp written in lisp. William Byrd learned about it from Daniel P. Friedman (The Little Lisper, The Little Schemer, ....)

keithnz 8y ago

Alan Kay said :- (SF) If nothing else, Lisp was carefully defined in terms of Lisp. (AK) Yes, that was the big revelation to me when I was in graduate school—when I finally understood that the half page of code on the bottom of page 13 of the Lisp 1.5 manual was Lisp in itself. These were “Maxwell’s Equations of Software!” This is the whole world of programming in a few lines that I can put my hand over. https://queue.acm.org/detail.cfm?id=1039523 https://queue.acm.org/detail.cfm?id=1039523

WalterGR 8y ago
Preformatted text on HN is really hard to read on mobile. Reformatted: (SF) If nothing else, Lisp was carefully defined in terms of Lisp. (AK) Yes, that was the big revelation to me when I was in graduate school—when I finally understood that the half page of code on the bottom of page 13 of the Lisp 1.5 manual was Lisp in itself. These were “Maxwell’s Equations of Software!” This is the whole world of programming in a few lines that I can put my hand over. Page 13 of that manual is page 21 of this PDF: http://www.softwarepreservation.org/projects/LISP/book/LISP%201.5%20Programmers%20Manual.pdf http://www.softwarepreservation.org/projects/LISP/book/LISP%...
ngcc_hk 8y ago
Hard to read when quote like this.

kazinator 8y ago

Lisp in Lisp interpreters actually have a marginal practical use. Suppose you've boostrapped a Lisp in some other language (assembly, C or whatever). You have an interpreter in that language, and have written a compiler for that Lisp in itself (say for a VM in that other language). You can now write an interpreter for that Lisp in itself. Once that interpreter behaves exactly like the original one in the other language, you can throw that one away. Bootstrapping can proceed by shipping the interpreter in compiled form. The benefit is that there is less language-processing code written in the other language. You could just throw the interpreter away and have a compiler only (bootstrapped with the compiled version of itself), but then it's useful to have two models of execution for programs.

bitwize 8y ago
This is how we got the first working Lisp implementations. John McCarthy specified Lisp in itself, and a graduate student translated it into IBM 704 assembly.

ncmncm 8y ago

At great risk of being downvoted to oblivion (before you pile on, check your motives), this struck me on first encounter, 30 years ago, and ever more strongly since, as the most self-indulgent of all programs. People impressed by it invariably appear, primarily, pleased with themselves for the depth of perception they demonstrate by being impressed with it. Comparing it to Maxwell's equations sharpens this. The equations are deeply illuminative of fundametal processes of reality, summarizing comprehensively and precisely decades of exacting experimentation by the best physicists of the age. The speed of light (in vacuum, and in any medium) is simply derived from them. No detail of them could be deduced without abstraction from all the experience of all who came before. How much work went into this program? Would any two people, who just knew Lisp, but no theory of computation, asked to write it, write it differently? How long could it take? An hour, a week, a month? How much insight would it take? How much lived experience does it represent? Think it through: A Lisp interpreter in Lisp. It demonstrates that, if you are handed a Lisp runtime, as we are today, it is easy to make it execute Lisp programs. With small changes, it runs slightly different programs. Should that impress us? Where did this Lisp runtime come from, and why would one expect it to be tuned for anything but running Lisp programs? If it were not good for running Lisp programs, what would it be good for? The program relies, fundamentally, on all the science (and, frankly, engineering) that came before, but illuminates none of it. It is a fleck of foam that rides determinedly at the surface, belying the depths that support it. It illuminates nothing beyond itself.

kazinator 8y ago
> Where did this Lisp runtime come from, and why would one expect it to be tuned for anything but running Lisp programs? In this case, it's running a program which very itself easily runs Lisp programs given to it as a source code data structure. That we normally don't expect. For instance, in C language run-time, though it of course supports running compiled C programs, it doesn't provide a straightforward way for one of these programs to itself process C programs. A C program that interprets a decent subset of C is pretty complicated. It has to provide a number of data structures, of course a parser (because C programs don't have a data structural representation) and memory management for the parse time and run-time and so on. The C-processing C program can't even ask for a function by name so that it could resolve a function call out to the native run-time. This is possible with some operating system extensions (dynamic symbols). That just solves the name resolution problem: then there is the problem of dynamically constructing the argument list for a function call and executing it. This requires a library not supplied in the C language such as GNU ffcall, or libffi. Think about it: a C interpreter for C needs to use a FFI mechanism (first F == foreign!) to expose the C run time to the interpreted C, and that FFI is far from a standard language feature. Lisp just resolves a symbol and calls apply and that's it; nothing is foreign: no visas have to be issued, no passports are stamped.