4 ms·

Oh, that would be a very strange interpretation of interpretation. I'm not sure what you mean by "reparsing code at runtime". Given that there isn't really a

by gdp 17y ago

Oh, that would be a very strange interpretation of interpretation. I'm not sure what you mean by "reparsing code at runtime". Given that there isn't really a "compile time" in a perl-like setting, when are you proposing the parsing happens?

chromatic 17y ago
Read the link. The poster suggested that Perl 5 subroutines take as an invisible argument the remaining source code (presumably from the end of the declaration of that sub to the end of the file) of the program so that they could reparse the remaining code when the subs evaluate to a known value. In Perl 5 parlance, "compile time" is when parsing happens. "Runtime" is when execution happens.
- gdp 17y ago
  Oh, I just read the comment you're referring to, and I think you've completely misinterpreted the commenter. The use of "program text" is used in a fairly precise way to mean "the tokens unconsumed up to this point in the execution", which appears to be what you asserted in your reply. Of course, given that the parse tree is just a structured representation of the program text, with no pre-determined traversal order, is it not true that the parser needs the context resulting from having evaluated part of the tree in order to decide how to proceed in evaluating the rest of it? I think you've taken a technically accurate comment and then answered a completely different point.
  - chromatic 17y ago
    The claim is that you must execute a Perl 5 subroutine to discover its arity. That's nonsense. In the general case, Perl 5 subroutines have well-defined arities: they consume as many arguments as possible, either delimited by parentheses or the statically-unambiguous end of an expression. In the special case of prototyped subroutines, the parser knows their arities as soon as it encounters their declarations. None of this has any connection to the claim that "it's necessary to execute the subroutine to discover just how many [tokens] it will consume." If that were true, perl -c would not work.

by gdp 17y ago

chromatic 17y ago

Read the link. The poster suggested that Perl 5 subroutines take as an invisible argument the remaining source code (presumably from the end of the declaration of that sub to the end of the file) of the program so that they could reparse the remaining code when the subs evaluate to a known value. In Perl 5 parlance, "compile time" is when parsing happens. "Runtime" is when execution happens.

gdp 17y ago
Oh, I just read the comment you're referring to, and I think you've completely misinterpreted the commenter. The use of "program text" is used in a fairly precise way to mean "the tokens unconsumed up to this point in the execution", which appears to be what you asserted in your reply. Of course, given that the parse tree is just a structured representation of the program text, with no pre-determined traversal order, is it not true that the parser needs the context resulting from having evaluated part of the tree in order to decide how to proceed in evaluating the rest of it? I think you've taken a technically accurate comment and then answered a completely different point.
- chromatic 17y ago
  The claim is that you must execute a Perl 5 subroutine to discover its arity. That's nonsense. In the general case, Perl 5 subroutines have well-defined arities: they consume as many arguments as possible, either delimited by parentheses or the statically-unambiguous end of an expression. In the special case of prototyped subroutines, the parser knows their arities as soon as it encounters their declarations. None of this has any connection to the claim that "it's necessary to execute the subroutine to discover just how many [tokens] it will consume." If that were true, perl -c would not work.