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Re^4: My problems to understand the Perl documentation

by haukex (Bishop)
on Aug 24, 2020 at 07:31 UTC ( #11121025=note: print w/replies, xml ) Need Help??


in reply to Re^3: My problems to understand the Perl documentation
in thread My problems to understand the Perl documentation

Is there any built-in without a prototype?

On 5.28, prototype returns undef for at least the following (I may have missed a few, and I omitted most things that I think most people would classify as keywords and operators instead of functions, like use, goto, and -X):

chomp chop defined delete do eval exec exists grep map print printf require return say select sort split system

Added minor clarifications.

Replies are listed 'Best First'.
Re^5: My problems to understand the Perl documentation
by LanX (Sage) on Aug 24, 2020 at 16:06 UTC
    > most people would classify as keywords and operators instead of functions

    For me any reserved word is a keyword, this includes functions.

    I know what you mean but "keyword" doesn't describe it.

    See also perlfunc#Perl-Functions-by-Category ... which is even more confusing.

    Cheers Rolf
    (addicted to the Perl Programming Language :)
    Wikisyntax for the Monastery

      Yes, good point, I was thinking of e.g. if and for, but I didn't list goto but did list return - now that I think about it some more, I probably shouldn't have listed the latter because it can't really be approximated by a sub (that's how I personally generally differentiate between "functions" and "operators" in Perl, but this isn't perfect and a pretty big grey area).

        In my book

        • (named) function something of the form Name(Args) usable as EXPR, that means returning a value at runtime. Parens can be omitted if precedence is clear. Arguments - if any - must follow to the right, either as one UNARY value or as comma separated LIST.
        • builtin : a named function in the language core. The name is a reserved keyword. Some may have special parsing rules for arguments and special context, such that they can't be replicated with sub (PROTOTYPE) { BLOCK }
        • operator symbols acting like functions by returning values but with "surrounding" (not necessarily following) arguments, special parsing and precedence like 2 * 3 . See perlop and overload
        • named operators like xor have an alphanumeric IDENTIFIER as "symbol". NB: some builtin functions are sometimes documented as "operators" (it's just a huge subgroup with a more standard syntax)
        • statement keywords anything requiring void context. I.e. can't be used in an expression (without do ). It usually follows a semicolon and is used for side-effects . Most at compile time like like use
        • Some of them are documented as "function-like keywords" because they parse like functions like my but are primarily used for declaration (a compile time side effect)

        Please expand/correct me. ..

        EDIT

        N.B. some keywords fall into multiple categories, depending on usage.

        sub name { Block } is a statement declaring a subroutine at compile time.

        $code = sub { Block }; is a builtin function returning a coderef at runtime.

        Cheers Rolf
        (addicted to the Perl Programming Language :)
        Wikisyntax for the Monastery

        To make things more complicated...

        Took a look into

        CORE

        and there "built-in functions" and "keywords" are used as synonyms. :/

        Cheers Rolf
        (addicted to the Perl Programming Language :)
        Wikisyntax for the Monastery

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