chap02 ex1 better implement

[amoszhou]

I think this is more better

[ryblovAV]

Hi @amoszhou,

a: =>A and b: =>B are by-name-parameters (not lazy values), they are evaluated every time when
they are used
In your solution they are executed twice

[amoszhou]

@ryblovAV yes you are right.
I just make the code looks like simple,! thanks you

[ryblovAV]

@amoszhou
You're welcome

[axel22]

@amoszhou Commeny from @ryblovAV is correct - the expression a is by name (not lazy), and it will be executed twice now. The first time in parallel in the thread statement, and the second time when returning from the method. This effectively removes parallelism, and if the a or b are side-effecting, will execute the side-effect twice.

If you want nicer code, you could do this:

lazy evaluatedA = a
lazy evaluatedB = b

val t1 = thread {
  evaluatedA
}
...
(evaluatedA, evaluatedB)

[amoszhou]

yes, thank you

[axel22]

You are welcome, just don't forget to add lazy vals and push again to sync the pull request if you made any changes.