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digitalmars.D.learn - int => struct cast

reply bearophile <bearophileHUGS lycos.com> writes:
Why can't I cast  an n int to a struct with only a x int field?
Time ago someone has said that all internal errors are problems, is this known
and bad?

struct S { int x; }
void main() {
    int n = 1;
    int[S] a;
    a[ cast(S)n ]++;
}

OUTPUT DMD 1.035:
temp.d(5): Error: e2ir: cannot cast from int to S
Internal error: e2ir.c 3904

Bye,
bearophile
Oct 02 2008
next sibling parent reply "Jarrett Billingsley" <jarrett.billingsley gmail.com> writes:
On Thu, Oct 2, 2008 at 10:04 AM, bearophile <bearophileHUGS lycos.com> wrote:

 Why can't I cast  an n int to a struct with only a x int field?
 Time ago someone has said that all internal errors are problems, is this known
and bad?

 struct S { int x; }
 void main() {
    int n = 1;
    int[S] a;
    a[ cast(S)n ]++;
 }

 OUTPUT DMD 1.035:
 temp.d(5): Error: e2ir: cannot cast from int to S
 Internal error: e2ir.c 3904

 Bye,
 bearophile



I'm guessing you can't do it because it doesn't make any sense.  Since
when did you expect this to work?  The typical solution is to cast
through a pointer, i.e. "*cast(S*)&n".

And yes, any time you see "internal error" put.  it.  in.  bugzilla.  please.
Oct 02 2008
parent bearophile <bearophileHUGS lycos.com> writes:
Jarrett Billingsley:

 I'm guessing you can't do it because it doesn't make any sense.  Since
 when did you expect this to work?  The typical solution is to cast
 through a pointer, i.e. "*cast(S*)&n".



The typical D solution here is probably:
a[ S(n) ]++;

Bye and thank you,
bearophile
Oct 02 2008
prev sibling next sibling parent =?UTF-8?B?QWxleGFuZGVyIFDDoW5law==?= writes:
bearophile wrote:

 Why can't I cast  an n int to a struct with only a x int field?



Why would you want to? This makes no sense.
Oct 03 2008
prev sibling parent reply Max Samukha <samukha voliacable.com.removethis> writes:
On Thu, 02 Oct 2008 10:04:18 -0400, bearophile
<bearophileHUGS lycos.com> wrote:


Why can't I cast  an n int to a struct with only a x int field?
Time ago someone has said that all internal errors are problems, is this known
and bad?

struct S { int x; }
void main() {
    int n = 1;
    int[S] a;
    a[ cast(S)n ]++;
}

OUTPUT DMD 1.035:
temp.d(5): Error: e2ir: cannot cast from int to S
Internal error: e2ir.c 3904

Bye,
bearophile



There is a not well documented feature that turns cast(S)n into S(n),
if opCall is defined

struct S {
  int x;
   static S opCall(int x) { S r; r.x = x; return r; } 
}

void main() {
    int n = 1;
    int[S] a;
    a[ cast(S)n ]++;
}
Oct 03 2008
parent bearophile <bearophileHUGS lycos.com> writes:
Max Samukha:

 There is a not well documented feature that turns cast(S)n into S(n),
 if opCall is defined



Cute, and unknown to me.

Thank you,
bearophile
Oct 03 2008