possen
(Paul Ossenbruggen)
1
So I have some code that utilizes structs, I would like to go through and update some of the values. While I could use map, it seems I should be able to do it using a for in loop without utilizing indexes. The mutate2 method uses enumerate, and the index to write back the copy to the array, but I would prefer to update the struct value itself and avoid having to use indexes as I try to avoid them, if possible.. It seems the structs kind of force you to go back to indexes. I was thinking that it would be useful to be able to apply the & (reference) operator here to allow direct access to the array element struct, an example of this is shown in mutate3. With a class this is not necessary. I know a little like C++ but just want to explore this idea unless there is some other way I missed.
struct Codon {
var val = Float(0.0)
var mask = false
}
class Geno {
var codons : [Codon]
// pure index based approach
func mutate() {
for i in 0..<codons.count {
if !codons[i].mask {
codons[i].val += r.gauss() * vari
}
}
}
// index to write back, less efficient?
func mutate2() {
for (index, var codon) in codons.enumerate() {
if !codon.mask {
codon.val += r.gauss()
codons[index] = codon
}
}
}
// suggested reference approach
func mutate3() {
for var &codon in codons {
if !codon.mask {
codon.val += r.gauss()
}
}
}
}
gribozavr
(Dmitri Gribenko)
2
This would be a useful extension to the language (but it is not clear
how to define it -- do we need to hardcode the knowledge about the
MutableCollection protocol into the compiler?)
There's something you can do today, though:
extension MutableCollectionType {
public mutating func mutatingEach(mutate: (inout Generator.Element) -> Void) {
for i in self.indices {
mutate(&self[i])
}
}
}
var a = [1,2,3]
a.mutatingEach { (x: inout Int) -> Void in x += 1 }
//a.mutatingEach { $0 += 1 } // does not work, probably due to a compiler bug.
print(a)
Dmitri
···
On Mon, Mar 7, 2016 at 12:57 AM, Paul Ossenbruggen via swift-evolution <swift-evolution@swift.org> wrote:
func mutate3() {
for var &codon in codons {
if !codon.mask {
codon.val += r.gauss()
}
}
}
}
--
main(i,j){for(i=2;;i++){for(j=2;j<i;j++){if(!(i%j)){j=0;break;}}if
(j){printf("%d\n",i);}}} /*Dmitri Gribenko <gribozavr@gmail.com>*/
pyrtsa
(Pyry Jahkola)
3
I don't disagree, but quick reminder: you might want to use `indices` instead of `..<`:
for i in codons.indices { codons[i] = ... }
— Pyry
···
On 07 Mar 2016, at 10:57, Paul Ossenbruggen via swift-evolution <swift-evolution@swift.org> wrote:
for i in 0..<codons.count { codons[i] = ... }
gribozavr
(Dmitri Gribenko)
4
func mutate3() {
for var &codon in codons {
if !codon.mask {
codon.val += r.gauss()
}
}
}
}
This would be a useful extension to the language (but it is not clear
how to define it -- do we need to hardcode the knowledge about the
MutableCollection protocol into the compiler?)
There's something you can do today, though:
extension MutableCollectionType {
public mutating func mutatingEach(mutate: (inout Generator.Element) -> Void) {
This method should be called 'mutateEach' to conform to the guidelines, though.
Dmitri
···
On Mon, Mar 7, 2016 at 2:24 AM, Dmitri Gribenko <gribozavr@gmail.com> wrote:
On Mon, Mar 7, 2016 at 12:57 AM, Paul Ossenbruggen via swift-evolution > <swift-evolution@swift.org> wrote:
for i in self.indices {
mutate(&self[i])
}
}
}
var a = [1,2,3]
a.mutatingEach { (x: inout Int) -> Void in x += 1 }
//a.mutatingEach { $0 += 1 } // does not work, probably due to a compiler bug.
print(a)
Dmitri
--
main(i,j){for(i=2;;i++){for(j=2;j<i;j++){if(!(i%j)){j=0;break;}}if
(j){printf("%d\n",i);}}} /*Dmitri Gribenko <gribozavr@gmail.com>*/
--
main(i,j){for(i=2;;i++){for(j=2;j<i;j++){if(!(i%j)){j=0;break;}}if
(j){printf("%d\n",i);}}} /*Dmitri Gribenko <gribozavr@gmail.com>*/
Joe_Groff
(Joe Groff)
5
This should be fixed in 7.3, for what it's worth.
-Joe
···
On Mar 7, 2016, at 2:24 AM, Dmitri Gribenko via swift-evolution <swift-evolution@swift.org> wrote:
var a = [1,2,3]
a.mutatingEach { (x: inout Int) -> Void in x += 1 }
//a.mutatingEach { $0 += 1 } // does not work, probably due to a compiler bug.
print(a)
possen
(Paul Ossenbruggen)
6
Thanks for pointing this out!
···
Sent from my iPhone
On Mar 7, 2016, at 10:11 AM, Pyry Jahkola <pyry.jahkola@iki.fi> wrote:
On 07 Mar 2016, at 10:57, Paul Ossenbruggen via swift-evolution <swift-evolution@swift.org> wrote:
for i in 0..<codons.count { codons[i] = ... }
I don't disagree, but quick reminder: you might want to use `indices` instead of `..<`:
for i in codons.indices { codons[i] = ... }
— Pyry
Joe_Groff
(Joe Groff)
8
Sounds like we have a regression in master, then. It worked for me in a 7.3 beta playground.
-Joe
···
On Mar 7, 2016, at 9:00 AM, Dmitri Gribenko <gribozavr@gmail.com> wrote:
On Mon, Mar 7, 2016 at 8:59 AM, Joe Groff <jgroff@apple.com> wrote:
On Mar 7, 2016, at 2:24 AM, Dmitri Gribenko via swift-evolution >> <swift-evolution@swift.org> wrote:
var a = [1,2,3]
a.mutatingEach { (x: inout Int) -> Void in x += 1 }
//a.mutatingEach { $0 += 1 } // does not work, probably due to a compiler
bug.
print(a)
This should be fixed in 7.3, for what it's worth.
I was testing on master.
