4 ms·

Somewhat related: Perl Cannot Be Parsed: A Formal Proof (2008) https://news.ycombinator.com/item?id=5770531 https://news.ycombinator.com/item?id=5770531

by saba2008 5y ago

rabbits77 5y ago
Well, to be a little pedantic, Perl cannot be statically parsed, since some constructs require runtime context. If it could not be parsed it could never work! And this is totally OK in my book, I use Perl for prototyping ideas and an expressive language that allows creativity from me the programmer is a feature as it promotes looking at a problem from multiple aspects.
- avgcorrection 5y ago
  “Cannot be X” most often means “in the general case”. (In the context of computability.)
- lmm 5y ago
  > Well, to be a little pedantic, Perl cannot be statically parsed, since some constructs require runtime context. If you're going to be pedantic, it's important to be correct; there's no such thing as dynamic parsing. > If it could not be parsed it could never work! What's the logic here? An interpreter doesn't have to operate on an AST, a language doesn't have to have a nontrivial grammar (consider Brainfuck). Perl is just a language in the same category: it doesn't have a (true) nontrivial AST, it doesn't have a (true) nontrivial grammar, and it can't be (truly, nontrivially) parsed.
  - samatman 5y ago
    > there's no such thing as dynamic parsing As long as we're indulging in pedantry, this is incorrect presuming dynamic means what it usually means. Any regular expression constructed at runtime contradicts you. Modifying your core parser at runtime though, who would do such a thing? Other than reader macros in Common Lisp I mean. Are we going to argue this means Common Lisp doesn't parse if we add reader macros at runtime? A peculiar argument. Now. Should we talk about whether doing that is a good idea? A lovely and separate conversation. I agree with GP that since Perl will spit out a parse tree, it does in fact parse, and since it's not static, well, it's dynamic. Which we can prove by, I dunno, writing some Perl which only parses on Fridays. Right?
    - lmm 5y ago
      > Are we going to argue this means Common Lisp doesn't parse if we add reader macros at runtime? A peculiar argument. Peculiar how? Isn't that just common sense?
    - bmn__ 5y ago
      > Modifying your core parser at runtime though, who would do such a thing? Perl? Its numerous language extensions allowed it to stay competitive for such a long time. Every time someone says "language X can do Y but Perl doesn't have that syntax", a new CPAN module is born to amend the shortcoming.

Somewhat related: Perl Cannot Be Parsed: A Formal Proof (2008) https://news.ycombinator.com/item?id=5770531 https://news.ycombinator.com/item?id=5770531

rabbits77 5y ago

Well, to be a little pedantic, Perl cannot be statically parsed, since some constructs require runtime context. If it could not be parsed it could never work! And this is totally OK in my book, I use Perl for prototyping ideas and an expressive language that allows creativity from me the programmer is a feature as it promotes looking at a problem from multiple aspects.

avgcorrection 5y ago
“Cannot be X” most often means “in the general case”. (In the context of computability.)
lmm 5y ago
> Well, to be a little pedantic, Perl cannot be statically parsed, since some constructs require runtime context. If you're going to be pedantic, it's important to be correct; there's no such thing as dynamic parsing. > If it could not be parsed it could never work! What's the logic here? An interpreter doesn't have to operate on an AST, a language doesn't have to have a nontrivial grammar (consider Brainfuck). Perl is just a language in the same category: it doesn't have a (true) nontrivial AST, it doesn't have a (true) nontrivial grammar, and it can't be (truly, nontrivially) parsed.
- samatman 5y ago
  > there's no such thing as dynamic parsing As long as we're indulging in pedantry, this is incorrect presuming dynamic means what it usually means. Any regular expression constructed at runtime contradicts you. Modifying your core parser at runtime though, who would do such a thing? Other than reader macros in Common Lisp I mean. Are we going to argue this means Common Lisp doesn't parse if we add reader macros at runtime? A peculiar argument. Now. Should we talk about whether doing that is a good idea? A lovely and separate conversation. I agree with GP that since Perl will spit out a parse tree, it does in fact parse, and since it's not static, well, it's dynamic. Which we can prove by, I dunno, writing some Perl which only parses on Fridays. Right?
  - lmm 5y ago
    > Are we going to argue this means Common Lisp doesn't parse if we add reader macros at runtime? A peculiar argument. Peculiar how? Isn't that just common sense?
  - bmn__ 5y ago
    > Modifying your core parser at runtime though, who would do such a thing? Perl? Its numerous language extensions allowed it to stay competitive for such a long time. Every time someone says "language X can do Y but Perl doesn't have that syntax", a new CPAN module is born to amend the shortcoming.