• Spacen Jasset (7/7) Jan 10 2008 If I have:
• Christopher Wright (10/20) Jan 10 2008 A float[4][4] is an array of four float[4]s.
• Spacen Jasset (4/28) Jan 10 2008 I see yes. I will develop a class I think instead of trying to quickly
• Jarrett Billingsley (4/8) Jan 10 2008 Actually, float[4][4] is 16 consecutive floats in memory. Static arrays...
• Spacen Jasset (3/16) Jan 10 2008 I see, that is what I wondered. I will however do something more
• Don Clugston (7/27) Jan 10 2008 No it isn't. It's a array of four floats, a simple block of memory.
• torhu (14/21) Jan 10 2008 That will work just fine, since those arrays have the same memory

Spacen Jasset <spacenjasset yahoo.co.uk> writes:

If I have:

float[16]	a;

can I cast it like this cast(float[4][4])a and pass it into a function 
expecting a float[4][4] or will this not work properly. It seems there 
is a problem doing so.

This is for working with matricies so I should most probably write some 
sort of class to allow row and columns access

Christopher Wright <dhasenan gmail.com> writes:

Spacen Jasset wrote:
 If I have:
 
 float[16]    a;
 
 can I cast it like this cast(float[4][4])a and pass it into a function 
 expecting a float[4][4] or will this not work properly. It seems there 
 is a problem doing so.
 
 This is for working with matricies so I should most probably write some 
 sort of class to allow row and columns access

A float[4][4] is an array of four float[4]s.
A float[4] is a (length, pointer) pair.

If multidimensional arrays are added (not just arrays of arrays), you'd 
get the syntax float[4,4], most likely.

If you want to keep the same memory, you can do:
float[16] flat;
float[4][4] square = [flat[0..4], flat[4..8], flat[8..12], flat[12..$]];

This isn't very pretty, but it grows at sqrt(N) for an original array of 
N elements, so it might be doable for your stuff.

Spacen Jasset <spacenjasset yahoo.co.uk> writes:

Christopher Wright wrote:
 Spacen Jasset wrote:
 If I have:

 float[16]    a;

 can I cast it like this cast(float[4][4])a and pass it into a function 
 expecting a float[4][4] or will this not work properly. It seems there 
 is a problem doing so.

 This is for working with matricies so I should most probably write 
 some sort of class to allow row and columns access

 
 A float[4][4] is an array of four float[4]s.
 A float[4] is a (length, pointer) pair.
 
 If multidimensional arrays are added (not just arrays of arrays), you'd 
 get the syntax float[4,4], most likely.
 
 If you want to keep the same memory, you can do:
 float[16] flat;
 float[4][4] square = [flat[0..4], flat[4..8], flat[8..12], flat[12..$]];
 
 This isn't very pretty, but it grows at sqrt(N) for an original array of 
 N elements, so it might be doable for your stuff.

I see yes. I will develop a class I think instead of trying to quickly 
do the aforementioned cast.

Thanks.

"Jarrett Billingsley" <kb3ctd2 yahoo.com> writes:

"Christopher Wright" <dhasenan gmail.com> wrote in message 
news:fm53jh$1r5k$1 digitalmars.com...

 A float[4][4] is an array of four float[4]s.
 A float[4] is a (length, pointer) pair.

 If multidimensional arrays are added (not just arrays of arrays), you'd 
 get the syntax float[4,4], most likely.

Actually, float[4][4] is 16 consecutive floats in memory.  Static arrays of 
static arrays are treated as rectangular arrays. 

Spacen Jasset <spacenjasset yahoo.co.uk> writes:

Jarrett Billingsley wrote:
 "Christopher Wright" <dhasenan gmail.com> wrote in message 
 news:fm53jh$1r5k$1 digitalmars.com...
 
 A float[4][4] is an array of four float[4]s.
 A float[4] is a (length, pointer) pair.

 If multidimensional arrays are added (not just arrays of arrays), you'd 
 get the syntax float[4,4], most likely.

 
 Actually, float[4][4] is 16 consecutive floats in memory.  Static arrays of 
 static arrays are treated as rectangular arrays. 
 
 

I see, that is what I wondered. I will however do something more 
'proper' for what I want to do finally.

Don Clugston <dac nospam.com.au> writes:

Christopher Wright wrote:
 Spacen Jasset wrote:
 If I have:

 float[16]    a;

 can I cast it like this cast(float[4][4])a and pass it into a function 
 expecting a float[4][4] or will this not work properly. It seems there 
 is a problem doing so.

 This is for working with matricies so I should most probably write 
 some sort of class to allow row and columns access

 
 A float[4][4] is an array of four float[4]s.
 A float[4] is a (length, pointer) pair.

No it isn't. <g> It's a array of four floats, a simple block of memory.
The cast should be fine. PROVIDED that you stick to static arrays (ie, all 
dimensions specified at compile time).

 If multidimensional arrays are added (not just arrays of arrays), you'd 
 get the syntax float[4,4], most likely.
 
 If you want to keep the same memory, you can do:
 float[16] flat;
 float[4][4] square = [flat[0..4], flat[4..8], flat[8..12], flat[12..$]];

You're thinking of
float [][4] square = [flat[0..4], flat[4..8], flat[8..12], flat[12..$]];

With float[4][4] there's no problem.

torhu <no spam.invalid> writes:

Spacen Jasset wrote:
 If I have:
 
 float[16]	a;
 
 can I cast it like this cast(float[4][4])a and pass it into a function 
 expecting a float[4][4] or will this not work properly. It seems there 
 is a problem doing so.

That will work just fine, since those arrays have the same memory 
layout.  But you might want to avoid such casts, since the compiler 
won't verify that the size of the array you're casting from actually 
matches the size of what you're casting to.

Static (meaning fixed-length) arrays are implicitly converted to dynamic 
arrays when used as an argument to a function that wants a dynamic 
array.  Then you can get hold of the true length of the argument inside 
the function, and do assert(a.length == 16).  Then you'll know it's safe 
to cast it to float[4][4].  But this is getting messy, so maybe a 
different way altogether is better.  Like wrapping a one-dimensional 
array in a struct with opIndex and opIndexAssign operators.

Scroll down to Rectangular Arrays on this page:
http://www.digitalmars.com/d/arrays.html