An interview with Larry Wall (LinuxVoice)

Posted Jul 24, 2015 12:03 UTC (Fri) by rsidd (subscriber, #2582)
In reply to: An interview with Larry Wall (LinuxVoice) by mchapman
Parent article: An interview with Larry Wall (LinuxVoice)

Because it may be a bug? Oversmartness is bad whether it's pwrl or MS Excel. When I try to add strings the compiler/interpreter should tell me and not silently change the type! There is a reason programs in Haskell tend to run correctly the first time.

An interview with Larry Wall (LinuxVoice)

Posted Jul 24, 2015 12:28 UTC (Fri) by mchapman (subscriber, #66589) [Link] (1 responses)

> Because it may be a bug?

It could be, yes. All code can be wrong.

I'm sure Perl 6 has a way to say "test that $a and $b are both Ints, throw an exception if they're not, otherwise add them together and, if the result can be stored in an Int, return that result, else throw an exception". You'll probably find it's a few more characters than + though.

An interview with Larry Wall (LinuxVoice)

Posted Jul 24, 2015 22:19 UTC (Fri) by raiph (guest, #89283) [Link]

Oh, I'm sure there are lots of ways. We're talking about Perl here. :)

The first thing I came up with:

($a,$b) ~~ :(Int, Int) or fail; $a + $b;

The `:(...)` bit is a literal signature, exactly like the ones that appear in function definitions. The `~~` "smartmatch" operator, with these operands, does a trial bind of the argument list on its left with the signature on its right.

I skipped testing the result because an Int can store arbitrarily large integers, and if all of RAM was consumed by a truly vast integer, an exception would (should) be raised by lower levels of the stack.

An interview with Larry Wall (LinuxVoice)

Posted Jul 24, 2015 21:21 UTC (Fri) by dvdeug (guest, #10998) [Link] (6 responses)

As the old quip goes "If you want Haskell, you know where to find it."* It really seems out of place in a subthread comparing Python and Perl.

* I found that frustrating in the early 90s, as C was widely available and PL/I was not.

An interview with Larry Wall (LinuxVoice)

Posted Jul 25, 2015 4:12 UTC (Sat) by rsidd (subscriber, #2582) [Link] (5 responses)

Python is heavily influenced by Haskell (indentation and list-comprehensions are two obvious examples). So it's not irrelevant.

An interview with Larry Wall (LinuxVoice)

Posted Jul 25, 2015 5:02 UTC (Sat) by dvdeug (guest, #10998) [Link] (4 responses)

Haskell's first release was in 1990; Python was created in 1990 and released in 1991. So it doesn't seem likely that indentation or any other early feature was influenced by Haskell. The type system, in particular, is very unHaskell. In these features, Perl and Python differ pretty marginally.

An interview with Larry Wall (LinuxVoice)

Posted Jul 25, 2015 11:56 UTC (Sat) by anselm (subscriber, #2796) [Link] (3 responses)

It's pretty safe to say that Python's use of indentation for structure was not a Haskell influence. This is fairly obvious considering that the ABC programming language, which Guido van Rossum worked on at CWI before starting Python, also used indentation for structure. ABC had been around for more than a decade before Python was released.

List comprehensions, OTOH, were only added to Python way later, namely with version 2.0, which was released in 2000. It would not be entirely unreasonable to consider them influenced by Haskell.

As far as the type systems of Perl and Python are concerned, I think there are considerable differences. The observation that Perl doesn't really differentiate between numbers and strings, calling them “scalars”, while in Python strings are a special case of a (“non-scalar”) container type that also includes tuples and lists would be one's first clue that the type systems of Perl and Python are not really very similar at all.

An interview with Larry Wall (LinuxVoice)

Posted Jul 25, 2015 12:37 UTC (Sat) by dvdeug (guest, #10998) [Link] (2 responses)

List comprehensions are listed as being derived from Haskell by one of the sources linked from Wikipedia. It's not that surprising a claim.

"Considerable" is in the eye of the beholder. When compared to Haskell, they look quite similar, both dynamic systems with heavy OO mixture and no type inference.

An interview with Larry Wall (LinuxVoice)

Posted Jul 26, 2015 3:19 UTC (Sun) by mathstuf (subscriber, #69389) [Link] (1 responses)

> no type inference

Maybe I'm just not parsing your statement properly, but Haskell does all kinds of type inference…

An interview with Larry Wall (LinuxVoice)

Posted Jul 26, 2015 18:47 UTC (Sun) by nix (subscriber, #2304) [Link]

Let's expand that sentence:

When compared to Haskell, Perl and Python look quite similar, both dynamic systems with heavy OO mixture and no type inference.