Add pop operation

[hea9549]

resolved: #125

details: implement pop opcode

I made a pop of vm. But I don't know if this is necessary.

• Test case

[boohyunsik]

if pop retuns err, why don't you return err?

[hea9549]

Do you mean stack.pop() throws an error? stack.pop() does not return an error.

[boohyunsik]

ah, I misunderstood :-D

[boohyunsik]

LGTM :-)

[hihiboss]

Is it really fine just removing item??

@hea9549 @boohyunsik @zeroFruit @leesd556 @junbeomlee

[AgwaB]

@hihiboss
I think it should be discussed especially with the compiler!

1. Is it ok just pop without error handling?
   -> EVM don't handle that error. why?

2. Is it ok just removing item ?
   -> EVM uses intPool, a temporary stack storage. why?

I'll register it to issue!

[hihiboss]

@leesd556

Ok. Thank you!

[hea9549]

@hihiboss
I think it should be discussed especially with the compiler!

1. Is it ok just pop without error handling?
   -> EVM don't handle that error. why?
2. Is it ok just removing item ?
   -> EVM uses intPool, a temporary stack storage. why?

I'll register it to issue!

1. I submit issue about this Requires a high-level opcode interface. #150

2. I found lot's of article about intpool. In my opinion, an intpool is simply used for reuse. also written in evm's intpool.go

// intPool is a pool of big integers that
// can be reused for all big.Int operations.

It is used to reuse objects without creating new ones.