Re: Hints Towards Writing a Module with New Operators

The little Fortran documentation that I can find by Googling suggests that, as moritz (implicitly) points out, .EQV. is just == on Booleans. If this is correct, are you just looking to bring to Perl the syntactic beauty of Fortran :-)—or is it that you want something that does the Boolean conversion for you, so that you can write $a .EQV. $b ^** as the equivalent of $a ? $b ? 1 : 0 : $b ? 0 : 1 ^*?

Either way, as moritz says, for adding new syntax to Perl-as-it-now-is, I think that the only options are ~~syntax filters~~ (struck out as I write it so that you don't even think about it) or Devel::Declare (which worries adamk).

^* Or ($a && $b) || !($a || $b), I suppose. UPDATE: Ha, and maybe I'd like to write my own routines for addition while I'm at it. Thanks, JavaFan. :-)

UPDATE: ^** Note that this precise syntax conflicts with string concatenation, but we shouldn't be using barewords anyway.

Comment on Re: Hints Towards Writing a Module with New Operators Select or Download Code

Replies are listed 'Best First'.
Re^2: Hints Towards Writing a Module with New Operators by JavaFan (Canon) on Dec 20, 2009 at 01:00 UTC
`!($a xor $b)` [download]	[reply] [d/l]
Re^3: Hints Towards Writing a Module with New Operators by BrowserUk (Patriarch) on Dec 20, 2009 at 01:03 UTC
Or .NEQV. ~= `$a ^ $b` .EQV. ~= `!($a ^ $b)` Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice. "I'd rather go naked than blow up my ass"	[reply] [d/l] [select]
Re^4: Hints Towards Writing a Module with New Operators by JadeNB (Chaplain) on Dec 20, 2009 at 01:13 UTC
Those aren't the same: `!(2 xor 1); # => 1 !(2 ^ 1); # => 0` [download]	[reply] [d/l]
Re^5: Hints Towards Writing a Module with New Operators by BrowserUk (Patriarch) on Dec 20, 2009 at 08:24 UTC
Re^2: Hints Towards Writing a Module with New Operators by ikegami (Patriarch) on Dec 20, 2009 at 08:48 UTC
You could also use `!$a == !$b` [download] but that relies on the fact than the true and false values returned by Perl ops are 1) always the same, and 2) numeric. `xor` is definitely the way to go. — They're also strings, but that's not relevant here.	[reply] [d/l] [select]
Re^2: Hints Towards Writing a Module with New Operators by swampyankee (Parson) on Dec 20, 2009 at 23:14 UTC
Considering `.EQV.` as `==` for booleans is more or less correct: `a .eqv. b` is true if a and b are either both true or both false, and it would result in false otherwise. Most modern Fortran compilers will squawk if either a or b isn't a boolean (Fortran `logical`), so a fragment like `logical boole integer int int = 42 boole = .TRUE. write(,) 'is int .eqv. boole true?', int .eqv. boole` [download] will cause a compile-time error, which is, on the whole, probably a good thing. As I said in my original post, I've been programming Fortran for quite a few years and never found a use for `.eqv.` or `.neqv.`. As an aside, Fortran is insensitive to case; I tend to use uppercase for Fortran keywords and lowercase for everything else. Information about American English usage here and here. Floating point issues? Please read this before posting. — emc	[reply] [d/l]


go ahead... be a heretic
	PerlMonks