Allen Wirfs-Brock wrote:
(Yet Another Wacky Syntax Idea)
Here is a relatively common coding pattern:
var a;
var obj = {
get a() {return a},
set a(v) {a=v}
};
Often the intent is that the variable a should only be used within the object
literal. The block scoping with let and do operator will allow the variable
and object literal to be group in this manner:
let obj = do {
let a;
({get a() {return a},
set a()v) {a=v}
})
}
Unfortunately, the object literal has to be enclosed in parentheses because an
expression statement cannot begin with an object literal. The same would be
the case if a function expression was involved rather than an object literal.
Parens are annoying because you have to remember to close them and match them
if any additional nesting is involved.
With completion reform, do expressions, and broader use of blocks that produce
values we should expect to see more situations where an ExpressionStatement
needs to start with an object literal or function expression. It would be nice
to have some way to do this that does not require parentheses.
Prefix the expression with an unary operator is sufficient to disambiguate such
expression but unfortunately all of the existing unary operators perform
conversions that would invalidate the value. However, a new unary operator
whose semantics was to simply return its operand value would do the job nicely.
Both . and = seem like good candidates for such an operator but any operator
symbol that is not currently used in a unary form would be a possibility:
let obj = do {
let a;
={get a() {return a},
set a(v) {a=v}
}
}
let obj = do {
let a;
.{get a() {return a},
set a(v) {a=v}
}
}
let obj = do {
let a;
^{get a() {return a}, //probably my favorite, but that may just be a
leakage from my Smalltalk background...
set a(v) {a=v}
}
}
let obj = do {
let a;
|{get a() {return a},
set a(v) {a=v}
}
}
let obj = do {
let a;
/{get a() {return a},
set a(v) {a=v}
}
}
let obj = do {
let a;
*{get a() {return a},
set a(v) {a=v}
}
}
Isn't this already doing it?
let obj = do {
let a;
0,{get a() {return a},
set a(v) {a=v}
}
}
So, just allow comma operator with empty LHS and you've got it:
let obj = do {
let a;
,{get a() {return a},
set a(v) {a=v}
}
}
Not nice. But logical.
Herby
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