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https://issues.apache.org/jira/browse/GROOVY-11525?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17904525#comment-17904525
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Eric Milles commented on GROOVY-11525:
--------------------------------------
[~blackdrag] One could not rewrite the original while loop in this way,
because "c" would only be available within its enclosing parens.
{code:groovy}
while ((char c; (c = stream.peek()) != ' ')) {
// cannot reference "c" here
}
{code}
{code:groovy}
char c
while ((c = stream.peek()) != ' ') {
// can reference "c" here
}
// can reference "c" here
{code}
That's why I think {{instanceof}} might get you most of the way:
{code:groovy}
while (stream.peek() instanceof char c && c != ' ') {
// can reference "c" here
}
// cannot reference "c" here
{code}
> Support expression scope variable
> ---------------------------------
>
> Key: GROOVY-11525
> URL: https://issues.apache.org/jira/browse/GROOVY-11525
> Project: Groovy
> Issue Type: New Feature
> Reporter: Daniel Sun
> Priority: Major
>
> Let's take a look at the following code first:
> {code}
> int hash(Object key) {
> int h;
> return (key == null) ? 0 : (h = key.hashCode()) ^ (h >>> 16);
> }
> {code}
> variable {{h}} is actually an expression scope variable, but current syntax
> doesn't support.
> I propose an expression scope variable syntax, e.g.
> Proposed syntax 1:
> {code}
> // Just support declaring variables of same type
> (int h, x, y; ...)
> {code}
> {code}
> int hash(Object key) {
> // h is only visible in the expression
> return (int h; (key == null) ? 0 : (h = key.hashCode()) ^ (h >>> 16))
> }
> {code}
> We can reduce the scope of {{h}} further:
> {code}
> int hash(Object key) {
> // h is only visible in the expression
> return (key == null) ? 0 : (int h; (h = key.hashCode()) ^ (h >>> 16))
> }
> {code}
> Proposed syntax 2(I prefer the syntax):
> {code}
> // Support declaring variables of different types
> (int h, X x, Y y -> ...)
> {code}
> {code}
> int hash(Object key) {
> // h is only visible in the expression
> return (int h -> (key == null) ? 0 : (h = key.hashCode()) ^ (h >>> 16))
> }
> {code}
> {code}
> int hash(Object key) {
> // h is only visible in the expression
> return (key == null) ? 0 : (int h -> (h = key.hashCode()) ^ (h >>> 16))
> }
> {code}
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