forEach no longer works with lambdas

[benmccann]

I tried upgrading Tablesaw from 7.2.1 to 8.1.1 and got the error below:

[ERROR] tablesaw/core/src/main/java/tech/tablesaw/api/IntColumn.java:[208,13] reference to forEach is ambiguous
both method forEach(java.util.function.IntConsumer) in it.unimi.dsi.fastutil.ints.IntIterable and method forEach(java.util.function.Consumer<? super java.lang.Integer>) in it.unimi.dsi.fastutil.ints.IntIterable match

Can the method forEach(java.util.function.Consumer<? super java.lang.Integer>) be removed so that we don't have ambiguous methods?

[vigna]

On 2 Dec 2017, at 03:56, Ben McCann ***@***.***> wrote: I tried upgrading Tablesaw from 7.2.1 to 8.1.1 and got the error below: [ERROR] tablesaw/core/src/main/java/tech/tablesaw/api/IntColumn.java:[208,13] reference to forEach is ambiguous both method forEach(java.util.function.IntConsumer) in it.unimi.dsi.fastutil.ints.IntIterable and method forEach(java.util.function.Consumer<? super java.lang.Integer>) in it.unimi.dsi.fastutil.ints.IntIterable match Can the method forEach(java.util.function.Consumer<? super java.lang.Integer>) be removed so that we don't have ambiguous methods?

Sigh. The generic forEach is a default method--there's little we can do. The simplest fix is to declare the lambda parameter: (int x) -> code. Ciao, seba

[vigna]

BTW, this message of yours highlighted a major problem with the "incremental implementation strategy" I'm using WRT Java 8 methods. Including new methods with specific lambdas will introduce source-code compilation incompatibilities. That's really bad.

[benmccann]

great, thanks! I wasn't quite sure of the syntax, so appreciate the help

I was able to complete the upgrade relatively easily jtablesaw/tablesaw@56221d1

[vigna]

Ouch. When we took the decision of not having a forEachInt() method I didn't realize that adapting the :: syntax would have been so painful. Maybe we took the wrong decision, but at this point unfortunately it will stay there for a long time :(.

[incaseoftrouble]

FYI: You should be able to write doubles.forEach((DoubleConsumer) column::append);. This way you can at least use method references ...

[vigna]

On 3 Dec 2017, at 09:35, Tobias Meggendorfer ***@***.***> wrote: FYI: You should be able to write doubles.forEach((DoubleConsumer) column::append);. This way you can at least use method references ...

Clearly, I need to study Java 8 better. :( Ciao, seba

[benmccann]

Is there any reason to prefer doubles.forEach((double i) -> column.append(i)); vs doubles.forEach((DoubleConsumer) column::append);? Are they equivalently performant?

[incaseoftrouble]

Short answer: No

Slightly longer answer: Maybe, but you shouldn't worry about it (see, e.g., https://softwareengineering.stackexchange.com/questions/277473 ). Using method reference makes potentially makes it easier for the compiler to figure out some optimizations.