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0 points · 0 comments · 9 years ago · fusiongyro

news.ycombinator.com/item?id=12741430

Knuth is simply defining a piecewise function here in ordinary math notation. Functional programming languages borrow heavily from math, Erlang is a functional language. The resemblance would probably be even more striking with Haskell... which only serves to undermine the message.

Erlang's great though. Glad to see some irrational exuberance for it.

erez9 years ago
I'm waiting for the sequel, Gutenberg used the same characters as in C, making him the first C programmer.
nayuki9 years ago
Knuth's function would be written in Haskell as thus:
f [n] = [n]
f [m, n] = [m, n, 0, 1]
f [m, n, r, 1] = [m, n, mod m n, 2]
f [m, n, r, 2] = if r == 0 then [n] else [m, n, r, 3]
f [m, n, p, 3] = [n, p, p, 1]
It needs to be implemented with variable-length lists instead of fixed-length tuples, in order to satisfy the type system.
old_sound9 years ago
With haskell it will be less similar since Haskell doesn't use the semi-colon to separate function clauses, and the period for delimit the last one. You could argue that Haskell tuples will use the () syntax instead of {} as in Erlang.
I've mostly wrote this joke since many Erlang beginners find the semi-colon/period syntax confusing, but then there you have it on an essential book about programming
krmboya9 years ago
Hence the 'platonic language ideal' that the author speaks about in the last paragraph?

news.ycombinator.com/item?id=12741430

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0 points · 0 comments · 9 years ago · fusiongyro

news.ycombinator.com/item?id=12741430

Erlang's great though. Glad to see some irrational exuberance for it.

erez9 years ago
I'm waiting for the sequel, Gutenberg used the same characters as in C, making him the first C programmer.
nayuki9 years ago
Knuth's function would be written in Haskell as thus:
f [n] = [n]
f [m, n] = [m, n, 0, 1]
f [m, n, r, 1] = [m, n, mod m n, 2]
f [m, n, r, 2] = if r == 0 then [n] else [m, n, r, 3]
f [m, n, p, 3] = [n, p, p, 1]
It needs to be implemented with variable-length lists instead of fixed-length tuples, in order to satisfy the type system.
old_sound9 years ago
With haskell it will be less similar since Haskell doesn't use the semi-colon to separate function clauses, and the period for delimit the last one. You could argue that Haskell tuples will use the () syntax instead of {} as in Erlang.
I've mostly wrote this joke since many Erlang beginners find the semi-colon/period syntax confusing, but then there you have it on an essential book about programming
krmboya9 years ago
Hence the 'platonic language ideal' that the author speaks about in the last paragraph?

news.ycombinator.com/item?id=12741430