Why the scalar types are not all discrete types ?

[Philippe Torres <ptorres@laas.fr>]

I don't understand very well...

For instance, the fixed-point types have the attributes First, Last but
Pos is not permitted (only for discrete types if i got it right). Why ?
Because Pos is an integer and the range of the fixed-point type can be
bigger than the range of type Integer ?

I ask that because i would like to iterate over a fixed-point index in a
'for ... loop' but the 'for ... loop' demands a 'range' over a discrete
type.

Quite weird for me since 'range' can be used in a fixed-point type
declaration :
---
type fixed_2_digits is delta 0.1 range -20.0 .. 20.0 ;
---
As usual, i must miss something somewhere...

Philippe