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digitalmars.D.learn - Casting gremlins

reply Todd <toddtitus mindspring.com> writes:
In C it was possible to cast a Uint to a Char[], however, I can't seem to get
it to compile in D. 

example: I have 

uint data1;
long data;
long lblonedata;
.
.
.
char[] dataone = cast(char[]) data1;
lblonedata = atoi(dataone);

I'm importing std.string, std.conv;

and get e2ir: cannot cast uint to char[]

I was using dmd 1.022 and switched to 2.x today with no help.
Does D use a different method? or I'm I missing something obvious?

Todd
'newest newbee'
Oct 10 2007
parent reply Frits van Bommel <fvbommel REMwOVExCAPSs.nl> writes:
Todd wrote:

 In C it was possible to cast a Uint to a Char[], however, I can't seem to get
it to compile in D. 
 
 example: I have 
 
 uint data1;
 long data;
 long lblonedata;
 .
 .
 .
 char[] dataone = cast(char[]) data1;
 lblonedata = atoi(dataone);
 
 I'm importing std.string, std.conv;
 
 and get e2ir: cannot cast uint to char[]
 
 I was using dmd 1.022 and switched to 2.x today with no help.
 Does D use a different method? or I'm I missing something obvious?


In C, an array is just a pointer. In D it also contains a length (unless 
it's a static array, in which case that's encoded in the type).
You could try casting to a pointer instead, but casting between pointer 
and non-pointer types usually means you're doing something wrong. What 
is it exactly that you're trying to achieve here?
Oct 10 2007
parent reply Todd <toddtitus mindspring.com> writes:
Frits van Bommel Wrote:


 Todd wrote:

 In C it was possible to cast a Uint to a Char[], however, I can't seem to get
it to compile in D. 
 
 example: I have 
 
 uint data1;
 long data;
 long lblonedata;
 .
 .
 .
 char[] dataone = cast(char[]) data1;
 lblonedata = atoi(dataone);
 
 I'm importing std.string, std.conv;
 
 and get e2ir: cannot cast uint to char[]
 
 I was using dmd 1.022 and switched to 2.x today with no help.
 Does D use a different method? or I'm I missing something obvious?


 
 In C, an array is just a pointer. In D it also contains a length (unless 
 it's a static array, in which case that's encoded in the type).
 You could try casting to a pointer instead, but casting between pointer 
 and non-pointer types usually means you're doing something wrong. What 
 is it exactly that you're trying to achieve here?


I have a function that returns an uint, we'll call it 'data1'. from there, I'm
trying to cast it to a char to insert into a textbox, similiar to 'mini-calc'.
I know it's simple, but it seems to be escaping me at the moment.

Thanks for the reply,
Todd
Oct 10 2007
next sibling parent BCS <BCS pathlink.com> writes:
Todd wrote:

 Frits van Bommel Wrote:
 
 

Todd wrote:


In C it was possible to cast a Uint to a Char[], however, I can't seem to get
it to compile in D. 

example: I have 

uint data1;
long data;
long lblonedata;
.
.
.
char[] dataone = cast(char[]) data1;
lblonedata = atoi(dataone);

I'm importing std.string, std.conv;

and get e2ir: cannot cast uint to char[]

I was using dmd 1.022 and switched to 2.x today with no help.
Does D use a different method? or I'm I missing something obvious?


In C, an array is just a pointer. In D it also contains a length (unless 
it's a static array, in which case that's encoded in the type).
You could try casting to a pointer instead, but casting between pointer 
and non-pointer types usually means you're doing something wrong. What 
is it exactly that you're trying to achieve here?


 
 
 I have a function that returns an uint, we'll call it 'data1'. from there, I'm
trying to cast it to a char to insert into a textbox, similiar to 'mini-calc'.
I know it's simple, but it seems to be escaping me at the moment.
 
 Thanks for the reply,
 Todd
 



do you expect this?:

uint i = 57;

char[] c = cast(char[])i;

writef("%s\n", c); // prints "57"

AFAIK C won't do this. D has a function to do it. look in std.string for 
toString(uint).
Oct 10 2007
prev sibling parent reply Christopher Wright <dhasenan gmail.com> writes:
Todd wrote:

 Frits van Bommel Wrote:
 

 Todd wrote:

 In C it was possible to cast a Uint to a Char[], however, I can't seem to get
it to compile in D. 

 example: I have 

 uint data1;
 long data;
 long lblonedata;
 .
 .
 .
 char[] dataone = cast(char[]) data1;
 lblonedata = atoi(dataone);

 I'm importing std.string, std.conv;

 and get e2ir: cannot cast uint to char[]

 I was using dmd 1.022 and switched to 2.x today with no help.
 Does D use a different method? or I'm I missing something obvious?


 In C, an array is just a pointer. In D it also contains a length (unless 
 it's a static array, in which case that's encoded in the type).
 You could try casting to a pointer instead, but casting between pointer 
 and non-pointer types usually means you're doing something wrong. What 
 is it exactly that you're trying to achieve here?


 
 I have a function that returns an uint, we'll call it 'data1'. from there, I'm
trying to cast it to a char to insert into a textbox, similiar to 'mini-calc'.
I know it's simple, but it seems to be escaping me at the moment.


You're speaking of casting, so I assume you want to print out the value 
of each byte. And if you're trying to make it human-readable, you'll 
have to convert it.

So, you want to change to ubyte. You have to use masks and shifts, or 
just shifts, for that, along with casts.

int i = someFunc();
ubyte[4] bytes;
bytes[0] = cast(ubyte)((i << 0)  >> 24);
bytes[1] = cast(ubyte)((i << 8)  >> 16);
bytes[2] = cast(ubyte)((i << 16) >>  8);
bytes[3] = cast(ubyte)((i << 24) >>  0);

Then to get a human-readable form of these, you can call 
std.string.toString on them.

If, however, you merely one a human-readable form of the integer, just 
use std.string.toString on it.


 Thanks for the reply,
 Todd
Oct 10 2007
parent Todd Titus <toddtitus mindspring.com> writes:
Christopher Wright Wrote:


 If, however, you merely one a human-readable form of the integer, just 
 use std.string.toString on it.


I used toString() on it. with the same results. I have found 2 additional
errors,(they multiply like rabbits).

1st. It compiles and links ok, and will output correctly non-stop, but if I
recompile it without making any changes it won't output. compile it again and
it works. seems like an inconsistent compile bug ??

2nd. I had to substitute a known value, (to bypass-rule out any hardware
issues) in the above compile. I found, or rather isolated it to an 'if'
statement that seems to mask the output. I'll try to narrow it down further in
the morning.
Oct 11 2007