What does -fm mean as a suffix for a runtime function name?

[Gregory Golberg]

Hi all,

Consider this example: https://play.golang.org/p/uy6rPFu6Z9

Which prints

main.Foo 

main.(*T).Bar-fm

What does -fm mean?

-g

[Matt Harden]

I'm not sure what it stands for (function from method?). But note that this is a Method Value https://golang.org/ref/spec#Method_values, so it's distinct from the method itself, which doesn't have a receiver already supplied.

https://play.golang.org/p/P2TELvh1Ho

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[Gregory Golberg]

Yes, it is noted - I specifically made this example like so. But why?

If I were to parse the Name() string I could still figure out that this is a method - because main.(*T).Bar-fm shows that it's on type T. 

So what's the point of the suffix?

[Matt Harden]

To distinguish it from main.(*T).Bar, which is a different thing (the method without receiver already supplied).

[Gregory Golberg]

Not really: https://play.golang.org/p/1-31t3prci ?

Gregory Golberg about.me/gregorygolberg

[Jakob Borg]

2016-07-06 7:10 GMT+02:00 Gregory Golberg <gri...@alum.mit.edu>:

Not really: https://play.golang.org/p/1-31t3prci ?

This is the difference Matt is referring to:

https://play.golang.org/p/MO_fEbZkeQ

//jb

[Gregory Golberg]

Ah, Jakob, thanks - did not see this before.

What's the semantic difference though, I'm not getting it.

[roger peppe]

The semantic difference is that Type.Method takes the receiver as its first argument, whereas value.Method does not (the value is part of the closure context, which is why creating a function in this way incurs an allocation).

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[Gregory Golberg]

Ah got it , thanks... 

To clarify for others: https://play.golang.org/p/opxR_ZpX3R