On 04/01/2014 11:28 AM, Bruce Chapman wrote:
Slightly preceding Ulf's coin proposal by a few hours was
http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/001134.html
Where I suggested the "naked dot" notation (coined in
http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/000855.html) has
better value as ".. a
syntax for referring to the receiver of a method inside arguments to the
method."
More formally, the naked dot (at the start of an expression, not
following an invocation to a void method) would refer to the receiver
of the innermost surrounding invocation expression.
A: What is the receiver of the invocation of a static method?
B: What is the receiver of the invocation of a constructor?
Regards, Peter
and so to answer Guy's question below in terms of my original
intention rather than Ulf's proposal, .indexof("Q") would use
myVeryLongNamedString as its receiver.
I see particular value for these naked dot expressions in creating
fluent APIs such as builder patterns. As suggested in my coin post,
there is also value for passing enums or named constants to methods
when (as is often the case) these named constants are defined in the
same class as the method being invoked. In a highly informal sense,
the naked dot enables on demand changing of the scope to be that of
the invocation expression's receiver,
I think with this interpretation of the meaning of naked or leading
dot, Guy's compromise restriction below is not required.
Bruce
On 27/03/2014 4:51 a.m., Guy Steele wrote:
I am a bit more skeptical about expressions that begin with a dot
because of potential
confusion about which expression is referred to:
myVeryLongNamedString.subString(.indexOf("C”), .indexOf("Q”))
seems clear enough, but what about:
myVeryLongNamedString.subString(.indexOf("C”) +
otherString.length(), .indexOf("Q”))
Does the second occurrence of .indexOf use myVeryLongNamedString or
otherString?
A compromise would be to allow leading-dot expressions to occur only
within the arguments
of the method call whose target is the object which the leading-dot
expressions are expected
to use as their target, and if there are such leading-dot expressions
within the arguments
then the arguments must not contain any non-leading-dot field
references or method calls.
Just a thought for discussion. This would be considered a separate
mechanism from the
chaining-of-void-methods mechanism (it was a very clever idea to try
to unify them in Ulf's
original proposal, though).
—Guy
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