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Postings from April 2001
THESE ARE NOT THE SAME TIRED ARGUMENTS! If you're on p5p, you're probably already rolling your eyes. However, I searched p5p all the way back to 1997 and could not find this proposal anywhere. Even though it looks similar to the standard "Java + concat overload" stuff, it is not, so please try to keep an open mind. Everyone agrees that keeping string and numeric ops semantically separate is a Good Thing. As Dave nicely explained, this allows us to twist our scalars into strings or numbers based on the operators, instead of the other way around. This allows a single scalar type. This is not something we want to lose. Under this proposal, string concatenation would be acheived by the *combination* of "" and +. So, in Perl 5 you would have something like this: $string3 = $string1 . $string2; In Perl 6, you would do this like so: $string3 = "$string1" + "$string2"; Here's the key: The quotes are REQUIRED. 100%. Always. If you left them off, you'd get numeric addition. Always. There is no magic type inference. Think of this like using $ and [] to get an array element. You can't just say 'array[1]' or '$array' and expect to get the right thing. Rather, you have to combine the two. Same here, you have to combine "" and +. The win here with Perl is that having $prefixes actually allows us to expand variables in "" still. No other HLL can do that. As such, other languages have to overload their operators based on type. In Perl, we can maintain the semantics of a separate string concat by requiring quotes. This is hardly a far cry from current; in fact, it's quite logical (since "" is already string context) and very close syntactically to other HLL's. So, here's a little table: Perl 5 Perl 6 --------------- --------------- -> . + + . "" and + You get a Java/Python/etc syntax while retaining the semantics of separate string and numeric ops. More Details ------------ Ok, if you're still reading, cool. Let's get down to the nitty-gritty. Here are some more examples of code: Perl 5 Perl 6 ----------------------------- ---------------------------- $res = $var + $var2; $res = $var + $var2; $name = "This" . "that"; $name = "This" + "that"; $name = "This" . $that; $name = "This" + "$that"; print "Next is " . $i + 1; print "Next is " + $i + 1; $me = $name . getpwuid($<); $me = "$name" + getpwuid($<); That last one is important. Notice that the "" on the $name means that the next + becomes a string concat. The getpwuid call is then concat'ed onto that. If, instead, you wrote: $me = $name + getpwuid($<); You would get numeric addition. Always. In this way, you maintain a reliable semantic separation of string concat and numeric addition, while gaining a syntax that is similar to other HLL's. Having "$var" expand $var is the reason this is possible. Anyways, what do you think? (Please try to resist knee-jerk Java reactions :). -Nate P.S. I've got many more examples, but didn't want to flood the list with a massive proposal. I'm pretty sure all the bases are covered, but am interested in potential gotcha's... P.P.S. I'm also not some Java newbie who's complaining about "." and "eq", so don't even go there.Thread Next