Re: Is s[1..0] legitimate?

Peter N Lewis wrote:

Is a zero length slice a legitimate structure?

Ie

var s, t: String(10); begin if EQ( s[1..0], t[1..0] ) then begin WriteLn( 'TRUE' ); end; end.

Should that work?

No:

: substring­variable = string­variable : `[' index­expression `..' index­expression `]' . : : The index­expressions in a substring­variable shall possess the : integer­type. It shall be an error if the string­variable of the : substring­variable is undefined, or if the value of an index­expression in a : substring­variable is less than 1 or greater than the length of the value of : the string­variable of the substring­variable, or if the value of the first : index­expression is greater than the value of the second index­expression.

Currently it gives

testpas.pas:6: size of array is too large

Fixed in the next release. (peter2*.pas)

however, if the 0 is changed to a runtime variable:

var s, t: String(10); n: Integer; begin n := 0; if EQ( s[1..n], t[1..n] ) then begin WriteLn( 'TRUE' ); end; end.

Then it returns TRUE (as expected, sort of).

Similarly for s := t[1..0]; etc.

So, is it legitimate or not? If it is, the compile error is a bug. If not, then there seems to be a missing runtime range check error (or do I have to enable that)?

Missing runtime range checks are one of the most well-known issues of GPC (even if not strictly a bug, as long as it's documented).

Frank