Logic...

Johan Schoeman

Johan Schoeman

Expert
Licensed User
Longtime User
B4X: 
If 0 = kvs.Get("flag") Then

This just goes against my "old" train of thought.... if not doing it this way but traditional way I get a warning in the IDE.

This makes sense to me....

B4X: 
If kvs.Get("flag") = 0 Then
 
This is a kind of reverse logic (probably of "volcanic" origin).
In any case, my logical thinking does not work like that. I compare a term with a value and not vice versa. However, it is a mathematical equation in the end. Even more so with a test for an absolute value it becomes more strange.
But every now and then I have stumbled across the IDE pointing this out to me.

Live long and prosper...
 
BlueVision said:
This is a kind of reverse logic (probably of "volcanic" origin).
In any case, my logical thinking does not work like that. I compare a term with a value and not vice versa. However, it is a mathematical equation in the end. Even more so with a test for an absolute value it becomes more strange.
But every now and then I have stumbled across the IDE pointing this out to me.

Live long and prosper...
Click to expand...
It is probably like a RPN calculator. Takes some time to get used to it vs a traditional calculator. I use to own a HP41CX calculator but lost it when they broke into my car when I stopped at a shop on my way home from work and me being inside the shop (it is just how SA is). Now I have a HP41 app on my cell. So used to using RPN over the last 40 odd years that I battle to use a standard calculator.
 
Last edited:
LOL...
And I have deliberately avoided the comparison with reversed Polish notation. That came to me right away, too. Shame on you! :eek:
 
B4X: 
If 0 = kvs.Get("flag") Then
This is similar to:
B4X: 
If kvs.Get("flag") == 0 Then
in other language.
This is Erel's decision not to make B4X more complex by introducing a new operator.
 
Some clarifications:
The compiler uses the left hand side value to determine the comparison type. In this case the compiler cannot know the type and therefore the type must match exactly.
Example:
Code: 
Dim d As Double = 0
Dim map As Map = CreateMap("test": d)
Log(map.Get("test") = 0) 'false
Log(0 = map.Get("test")) 'true
Log(map.Get("test").As(Int) = 0) 'true

This was always the behavior. The warning is relatively new.
 
I have had a hard time adjusting as well, but read Erel's post. It makes sense and I am glad the warning is there. I have had errors when the number was returned as a string and hence - no match. Not so with the number first.
 
Last edited:
You must log in or register to reply here.
Back
Top