MG,
the idea is very plain:
- if you don't need to nest same-named variables, there's no harm, you just
don't do that, and all's well and swell — the danger you do that inadvertently
and mess up your code is nonzero, but extremely small;
- if you happen to need that — typically, if you are copy-pasting some
well-tested inner code into another method — you just do that and don't have to
rename. And that's highly desirable, for renaming is dangerous and error-prone:
you rename once-too-many or once-too-less, and hard-to-find errors ensue.
As for coding style, that's in the eye of the beholder, but in my own
experience, it is considerably better to keep the same approach — like i, j, k
etc. for indices used in small loops etc. — than using i here, i1 there, i2 in
just another place, all messing up the code mightily, without any proper reason
— just forced by the compiler deficiency in proper nesting.
Incidentally, Groovy sort-of supports this with it: you can write
3.times { // works all right, which is, well... all right :)
println "outer: $it"
it.times {
println "inner: $it all right"
}
}
it is completely absurd and nonsensical that you can not rewrite the very and
completely same code with explicit variables:
3.times { n -> // does not work, which is wrong
println "outer: $n"
n.times { n ->
println "inner: $n oops!"
}
}
This “let's try to prevent the programmer shooting his own leg by crippling his
gun” approach of Java is actually a cause of infinitely more errors than those
it prevents. We should leave it to Java to cherish its terrible design howlers
— and get rid of them in Groovy, in my personal opinion :)
All the best,
OC
> On 2 Dec 2020, at 23:33, MG <[email protected]> wrote:
>
> Hi OC,
>
> I think that generally speaking, hiding/masking an outer variable like that
> is a quite undesireable coding style, so I like the current Groovy behavior
> (even if it deviates from C, evidently - I never used code like that in C, so
> I did not even know it was valid ;-) ).
>
> What specific use case did you have in mind, where just renaming the inner
> variable to i0, j, k, ... or the outer to index, idx, ... would not be the
> better solution ?
> (I use an informal coding style where I use variable names with a number at
> the end for short term / loop / etc variables, and for parameters and
> variables who live throughout a method or larger block I use no number
> postfix or longer names; the short name / long name meta at least is quite
> common, I think)
>
> Cheers,
> mg
>
>
> On 02/12/2020 18:13, OCsite wrote:
>> Hello there,
>>
>> when touching this stuff, it would be extremely desirable primarily to fix
>> the scoping/obscuring of same-named variables, which Groovy at the moment
>> does wrong, same as the demented Java thing:
>>
>> ===
>> 89 ocs /tmp> <q.groovy
>> def i=0 // outer
>> println "i=$i (outer)"
>> for (int i=1 /* inner */;i<2;i++) println "i=$i (inner)"
>> println "i=$i (outer again)"
>> 89 ocs /tmp> /usr/local/groovy-4.0.0-alpha-1/bin/groovy q
>> org.codehaus.groovy.control.MultipleCompilationErrorsException: startup
>> failed:
>> /private/tmp/q.groovy: 3: The current scope already contains a variable of
>> the name i
>> @ line 3, column 10.
>> for (int i=1 /* inner */;i<2;i++) println "i=$i (inner)"
>> ^
>> 1 error
>> 90 ocs /tmp>
>> ===
>>
>> This is how it should work:
>>
>> ===
>> 90 ocs /tmp> <q.c
>> #include <stdio.h>
>> int main() {
>> int i=0;
>> printf("i=%d (outer)\n",i);
>> for (int i=1 /* inner */;i<2;i++) printf("i=%d (inner)\n",i);
>> printf("i=%d (outer again)\n",i);
>> return 0;
>> }
>> 91 ocs /tmp> cc -Wall q.c && ./a.out
>> i=0 (outer)
>> i=1 (inner)
>> i=0 (outer again)
>> 92 ocs /tmp>
>> ===
>>
>> Thanks and all the best,
>> OC
>>
>>> On 2 Dec 2020, at 17:34, Milles, Eric (TR Technology)
>>> <[email protected] <mailto:[email protected]>>
>>> wrote:
>>>
>>> Traditional "for" (first example) and ARM "try" (last example) support
>>> local variable declarations that are scoped to the statement. In light of
>>> the upcoming "instanceof" enhancement in Java, I was
>>> thinking about possible alternatives for declaring local variables that
>>> have statement scope.
>>>
>>> for (int i = ...; ...) {
>>> // i available
>>> }
>>> // i unavailable
>>>
>>> for (x in y index i) { // from Gosu (http://gosu-lang.github.io/docs.html
>>> <http://gosu-lang.github.io/docs.html>) -- an alternative to using
>>> eachWithIndex
>>> }
>>>
>>> if (x instanceof T t) { // from Java 14+
>>> }
>>>
>>> if (def x = ...) { // tests Groovy truth in this form; may be wrapped in
>>> parens to check something else about "x"
>>> }
>>>
>>> try (def ac = ...) {
>>> }
>>>
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>
