loop x in [a->b] tags x as constant but remains set after loop exits about ceu HOT 1 OPEN

The compiler already refuses to initialize or assign variables later used in loop, reporting that they are read-only. So I was wrong when I said "x is mine".

var int x = 7; // invalid assignment : read-only variable "x"
loop x in [2->8] do ... end

Hence what's left of this issue is:

1. Bug: The compiler should detect and prevent the nested loop example.
2. Enhancement: Make the loop variable unreadable after loop exit, to avoid undefined behaviour and thus non-determinism. (Alternatively try really hard to precisely define the value. Not trivial with C as a backend, where lots of simple operations cause undefined behaviour, e.g. signed addition overflow.)
3. Enhancement: Syntax loop var int x in ... which would avoid all these pitfalls.

Meanwhile, one can take advantage of the current behaviour to provide immutable variables to Céu:

#define constvar(typ,name,value) \
  var typ name; \
  loop/1 name in [ (value) -> _] do break; end
constvar(uint, x, 1+2*3);
_printf("%u\n",x);
//x = 7; // invalid assignment : read-only variable "x"

Alas, vec[x] is still not the same as vec[7] (dynamic vs. static allocation). That would require real support for constants in Céu.

from ceu.