[Wish] Inline Operators

[Roger Garstang]

The closer we get to OO the more can be done inline. One thing I like in other languages/environments is commands that can be done inline. In BASIC it is sometimes called Inline IF of IIF...C++/C# calls it various things but we used to call it the Huh? Operator because it uses a ? like- (BooleanTest) ? ReturnIfTrue : ReturnIfFalse. C# even has a ?? operator which is cool that test for null like X = Y ?? 2 Where X is assigned Y unless Y is null then it is set to 2.

 

[imbault]

wish operators

I do agree.

other operators like
:= or =
+= -= ...
also ++ --

would be great:
better to write

dim a:=0 as int

a++

than
dim a as int
a=0
a=a+1

 

[Roger Garstang]

:=, boy that brings back memories. Last time I used that was in Pascal. I do kind of like it for assignment and = for boolean compares vs. the = and == stuff C++ type languages use. BASIC seemed to always stick with just an = which depended on how it was used, and really could have used a different way for one like using :=.

 

[barx]

The java language does have such operator, it's caller the ternary conditional operator with the format of

Val = (a > b)? a : b

How difficult it would be to bring this forward to b4a and the practicalities? I don't know?

 

[Roger Garstang]

Ternary, yes, I knew there was a name for them but the .NET docs kept just calling it conditional. I knew it ended in an "ary" but could only find unary which wasn't it (Although there was a suggestion for them above which would be a plus too).

 

[bartv]

I support these requests.
As there is an equivalent in underlying java, the ternary operator could be implemented in B4A in the spirit of VB6 :

Iif(condition, expr1, expr2)

 

[Erel]

IIF can be implemented this way:

Sub IIF(condition As Boolean, TrueValue As Object, FalseValue As Object)
 If condition Then return TrueValue Else Return FalseValue
End Sub 
'Example
y = IIF(x > 100, 10, x + 10)

 

[wonder]

IIF can be implemented this way:

@Erel, there is, however a BIG BIG problem with this code. Consider the following examples.

Java version:

x = (abc > xyz) ? Read_The_First_10000_Records_And_Find_X(databaseName) : Read_The_Last_10000_Records_And_Find_X(databaseName);

// Result A:
// [abc] is evaluated against [xyz]
// [abc] is greater than [xyz], the first branch is executed:
//     -> Analyze ten thousand records in search of X
//     -> Get X
//     -> THE END

// Result B:
// [abc] is evaluated against [xyz]
// [abc] is less than or equal to [xyz], the second branch is executed:
//     -> Analyze ten thousand records in search of X
//     -> Get X
//     -> THE END

// Record search cost: Between 1 and 10,000 iterations.

B4x version:

x = IFF(abc > xyz, Read_The_First_10000_Records_And_Find_X(databaseName), Read_The_Last_10000_Records_And_Find_X(databaseName))

'  Result A:
'  [abc] is evaluated against [xyz]
'      -> The result is passed as an argument to the IFF() method
'  The first ten thousand records are analyzed in search of X
'      -> The result is passed as an argument to the IFF() method
'  The last ten thousand records are analyzed in search of X
'      -> The result is passed as an argument to the IFF() method
'  In the IFF() method:
'  The first argument is TRUE:
'      -> Return the second argument
'      -> THE END

'  Result B:
'  [abc] is evaluated against [xyz]
'      -> The result is passed as an argument to the IFF() method
'  The first ten thousand records are analyzed in search of X
'      -> The result is passed as an argument to the IFF() method
'  The last ten thousand records are analyzed in search of X
'      -> The result is passed as an argument to the IFF() method
'  In the IFF() method:
'  The first argument is FALSE:
'      -> Return the third argument
'      -> THE END

'  Record search cost: Between 10,001 and 20,000 iterations.

I detected this problem in my own code, as I have been using the IFF() method for more than one year now...

Here's a practical crash/no crash example:

Dim x(5) As Int
'The array x is populated...
...
...
...

Dim y As Int
Dim a = Rnd(0, 10) As Int
'----------------------------------------------------------------
'No crash (SAFE)
    If a < x.Length Then
        y = x(a)
    Else
        y = -1
    End If
'----------------------------------------------------------------
'Potential crash (UNSAFE)
    y = IFF(a < x.Length, x(a), -1) 'CRASH for any value of a > 4
'----------------------------------------------------------------

So yeah... we need the real thing, a real implementation of "condition ? branch_a : branch_b".

 

[Erel]

That's true, the IIF code above is not short-circuited.

If it is problematic for your case then you shouldn't use it.
Note that regular conditions are short-circuited:

If a < x.Length AND x(a) = 100 Then 'this is safe

 

[wonder]

Yes indeed, nonetheless, will we ever get the real inline if?