igb@fulcrum.bt.co.uk (Ian G Batten) (09/27/89)
Should this code fragment compile under (1) pcc (2) an ANSI compiler?
int x;
switch (x)
{
case (int) 1:
printf ("1\n");
break;
case (int) 2:
printf ("2\n");
break;
}
At least one compiler here rejects this, saying the case does not reduce
to a constant expression. In fact, I suspect the general problem is
``is (int) constant a constant?''
ianhenry@utzoo.uucp (Henry Spencer) (09/30/89)
In article <62@masalla.fulcrum.bt.co.uk> igb@fulcrum.bt.co.uk (Ian G Batten) writes: >Should this code fragment compile under (1) pcc (2) an ANSI compiler? ... > case (int) 1: ... >At least one compiler here rejects this, saying the case does not reduce >to a constant expression. In fact, I suspect the general problem is >``is (int) constant a constant?'' In K&R1, the list of operators allowed in constant expressions did not include casts. This was probably an oversight (casts were a recent addition to the language at the time). Casts are legal there in ANSI C. -- "Where is D.D. Harriman now, | Henry Spencer at U of Toronto Zoology when we really *need* him?" | uunet!attcan!utzoo!henry henry@zoo.toronto.edu
matt@oddjob.uchicago.edu (Mens Sana in Campari Soda) (10/01/89)
igb@fulcrum.bt.co.uk (Ian G Batten) writes: ) >``is (int) constant a constant?'' henry@utzoo (Henry Spencer) writes: ) In K&R1, the list of operators allowed in constant expressions did not ) include casts. This was probably an oversight If you're thinking of buying any book on C, look to see how they define "constant expression". I looked in the local bookstore here and found a number of titles such as "Absolutely complete ultimate C book!" which either did not define the term at all or simply defined it as "any expression involving only constants." Bah! ________________________________________________________ Matt Crawford matt@oddjob.uchicago.edu