Author: larry Date: Fri Apr 7 12:26:35 2006 New Revision: 8608 Modified: doc/trunk/design/syn/S02.pod
Log: Simplified postfix/infix parsing policy to use "long dot". Modified: doc/trunk/design/syn/S02.pod ============================================================================== --- doc/trunk/design/syn/S02.pod (original) +++ doc/trunk/design/syn/S02.pod Fri Apr 7 12:26:35 2006 @@ -67,25 +67,49 @@ between postfix operators and infix operators, either of which may occur after a term. If a given token may be interpreted as either a postfix operator or an infix operator, the infix operator -requires space before it, and the postfix operator requires a lack -of space before it unless the previous token was follwed by a dot. -(Infix operators may not start with a dot.) In other words, the only -way to put whitespace before a postfix operator is to put whitespace -between a dot and the normal representation of the postfix operator. -In other other words, a postfix operator starting with a dot is allowed -to have any amount of whitespace between the dot and the rest of the -postfix operator. +requires space before it. Postfix operators may never have intervening +space, though they may have an intervening dot, or a "long dot" that begins +and ends with dots and contains whitespace and commentary between the dots. +The pattern for "long dot" is C<< m:p/\.+ \s<ws> \./ >>. (A minor +consequence of this is that the C<< postfix:<...> >> operator should not +be followed by whitespace.) For instance, if you were to add your own C<< infix:<++> >> operator, -then it must have space before it, and the normal autoincrementing -C<< postfix:<++> >> operator may not have space before it, or must -be written as C<$x. ++> instead. In standard Perl 6, however, it -doesn't matter if you put a space in front of C<< postfix:<++> >>. -To be future proof, though, you should omit the space or use dot. - -(A consequence of this rule is that a dot with whitespace in front of it -is always considered a method call on C<$_>. If a term is not expected at -this point, it is a syntax error.) +then it must have space before it. The normal autoincrementing +C<< postfix:<++> >> operator may never have space before it, but may +be written in any of these forms: + + $x++ + + $x.++ + + $x. .++ + + $x... .++ + + $x.................. .++ + + $x... + .++ + + $x... # comment + # more comment + .++ + + $x... # comment + =begin podstuff + whatever + =end podstuff + .++ + +A consequence of this rule is that, in the absence of a "long dot", +a dot with whitespace in front of it is always considered a method +call on C<$_> where a term is expected. If a term is not expected +at this point, it is a syntax error. (Unless, of course, there is +an infix operator of that name beginning with dot. You could define +a Fortranly C<< infix:<.EQ.> >>, for instance, if the fit took you. +But you'll have to be sure to always put whitespace in front of it, or +it would be interpreted as a postfix method call instead.) =item *
