Bounds / Limits Literal

[AdamSpeight2008]

Bound / Limits Literals

These allow the user to express a couple of values that are to be treated as a bounds or limits.
They can also express the (in/ex) clusivity of the each of those bounds or limits

Examples

 ~[[1 To 10]] ' 1 <= x <= 10    eg 1, 2, 3, 4, 5, 6, 7, 8, 9, 10
 ~[[1 To 10)] ' 1 <= x <  10    eg 1, 2, 3, 4, 5, 6, 7, 8, 9
 ~[(1 To 10]] ' 1 <  x <= 10    eg 2, 3, 4, 5, 6, 7, 8, 9, 10
 ~[(1 To 10)] ' 1 <  x <  10    eg 2, 3, 4, 5, 6, 7, 8, 9

 ~[[1 To 10 Step 2]] ' 1 <= x <= 10    eg 1, 3, 5, 7, 9
 ~[[1 To 10 Step 2)] ' 1 <= x <  10    eg 1, 3, 5, 7, 9
 ~[(1 To 10 Step 2]] ' 1 <  x <= 10    eg 2, 4, 6, 8, 10
 ~[(1 To 10 Step 2)] ' 1 <  x <  10    eg 2, 4, 6, 8

• It supports only two comparision operators equal to and not equal to.
• x = bounds equates to is x within the bounds?
• x <> bounds equates to is x not within the bounds?
• Implicitly convertable to an IEnumerable(Of T) IReadOnlyCollection(Of T)

Grammar [WIP]

          tilde ::= '~'
       range_op ::= 'To'
   range_values ::= expr ws+ range_op ws+ expr range_step?
     range_step ::= ws+ "Step" ws+ expr 
      range_box ::= '[' ws* clusivity_lower ws* range_values ws* clusivity_upper  ws* ']'
inclusive_lower ::= '['
exclusive_lower ::= '('
clusivity_lower ::= ( inclusive_lower | exclusive_lower )
inclusive_upper ::= ']'
exclusive_upper ::= ')'
clusivity_upper ::= ( inclusive_upper | exclusive_upper )
literal ::= ( tilde range_box )

[Bill-McC]

comments:
Really not VB'ish looking.
~ reminds me of not for some reason , or approximates
having to differentiate between ( and a [ to check for odd vs even --> aghh!!!

questions:
Is this for integer types only ?
Is this for comparison operations only as in For loops and If statements, or is it for assignment as well ?

[AdamSpeight2008]

An alternative is to use the range clause syntax eg `0 To 10' (restricting both bounds to inclusive)
Example

If x Is 1 To 10 Then Return "Valid" Else Return "Invalid" 

[rskar-git]

Maybe instead we can invent a Case function, somewhat like we have an If function:

If Case(x, 1 To 10) Then Return "Valid" Else Return "Invalid"

Anything that is fair game in the Case statement of a Select Case can be used:

If Case(x, Is > 0) Then Return "Valid" Else Return "Invalid"

Multiple conditions may be applicable:

If Case(x, 1 To 3, 99) Then Return "Valid" Else Return "Invalid"

(Above succeeds if between 1 and 3, or is equal to 99. As in, (x >= 1 AndAlso x <= 3) OrElse (x = 99).)

Perhaps two forms of Case? Single condition returns Boolean, multi condition returns Integer corresponding to the first succeeding condition (zero meaning no success)? E.g.:

If Case(x, 1 To 3, 99) > 0 Then Return "Valid" Else Return "Invalid"

Or instead, leave Case as a Boolean thing, and introduce Select function as the Integer thing? E.g.:

If Case(x, 1 To 3, 99) Then Return "Valid" Else Return "Invalid"
If Select(x, 1 To 3, 99) > 0 Then Return "Valid" Else Return "Invalid"

[AdamSpeight2008]

@rskar-git See newer proposal #160

[rskar-git]

@AdamSpeight2008 Thanks! (for proposal #160)