ISO Pascal reference manual

Appendix A
addition, any type which is a subrange of these is an ordinal type. Whenever
a type is used to select an object from a number of objects, an ordinal type is
required.
PROGRAM ok;
BEGIN
END.
TYPE colour = (red, yellow, green, blue);
VAR vector : ARRAY [colour] OF integer;
The error message is generated if an enumerated type is required and the
given type is not enumerated.
PROGRAM fail;
BEGIN
END.
TYPE enum1 = (alpha, beta, gamma);
VAR bad1 : ARRAY [real] OF integer; )real isn't ordinal}
good : SET OF enum1; [enuml is ordinal}
*ERROR 61 -- integer index types are not permitted
The compiler will not permit arrays to be declared where the type of the
index is integer. If it were to do so the program would require more
working memory than most computers can provide.
PROGRAM fail;
VAR a : ARRAY [integer] of char; (this would be huge}
BEGIN
END.
a[-maxint] := 'a';
a[+maxint] 'o';
*ERROR 62 -- an object of this type may not be given a '+' sign
*ERROR 62 -- an object of this type may not be given a '-' sign
Plus or minus signs may only be given to numerical objects. In particular
enumerated type and char type values may not be signed.
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