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digitalmars.D.learn - How can I check to see if template type is an array?

reply Tim <tim.oliver tutanota.com> writes:
Hi all,

I need to be able to check in a template whether the type given 
is an array type so that I can do some different logic. How can I 
do this? I would have thought that if(is(T == [])) would work, 
but no.


Thanks in advance
Jan 19 2021
next sibling parent Dennis <dkorpel gmail.com> writes:
On Tuesday, 19 January 2021 at 22:26:52 UTC, Tim wrote:

 I need to be able to check in a template whether the type given 
 is an array type so that I can do some different logic. How can 
 I do this?


`if(is(T == E[], E))` or `isDynamicArray!T` is you `import 
std.traits;`
Jan 19 2021
prev sibling parent reply Paul Backus <snarwin gmail.com> writes:
On Tuesday, 19 January 2021 at 22:26:52 UTC, Tim wrote:

 Hi all,

 I need to be able to check in a template whether the type given 
 is an array type so that I can do some different logic. How can 
 I do this? I would have thought that if(is(T == [])) would 
 work, but no.


 Thanks in advance


You've almost got it. The correct syntax is `is(T == U[], U)`. 
You can read it as "there exists some type U such that T == U[]".
Jan 19 2021
parent reply Tim <tim.oliver tutanota.com> writes:
On Tuesday, 19 January 2021 at 22:31:47 UTC, Paul Backus wrote:

 You've almost got it. The correct syntax is `is(T == U[], U)`. 
 You can read it as "there exists some type U such that T == 
 U[]".


Thanks! Do I need to specify U in the template function?
Jan 19 2021
parent reply Paul Backus <snarwin gmail.com> writes:
On Tuesday, 19 January 2021 at 22:34:04 UTC, Tim wrote:

 On Tuesday, 19 January 2021 at 22:31:47 UTC, Paul Backus wrote:

 You've almost got it. The correct syntax is `is(T == U[], U)`. 
 You can read it as "there exists some type U such that T == 
 U[]".


 Thanks! Do I need to specify U in the template function?


No, only inside the is(...) expression.
Jan 19 2021
parent reply Tim <tim.oliver tutanota.com> writes:
On Tuesday, 19 January 2021 at 22:36:47 UTC, Paul Backus wrote:

 On Tuesday, 19 January 2021 at 22:34:04 UTC, Tim wrote:

 On Tuesday, 19 January 2021 at 22:31:47 UTC, Paul Backus wrote:

 You've almost got it. The correct syntax is `is(T == U[], 
 U)`. You can read it as "there exists some type U such that T 
 == U[]".


 Thanks! Do I need to specify U in the template function?


 No, only inside the is(...) expression.


What if it is a static array i.e. double[3]?
Jan 19 2021
parent reply Paul Backus <snarwin gmail.com> writes:
On Tuesday, 19 January 2021 at 22:38:41 UTC, Tim wrote:

 On Tuesday, 19 January 2021 at 22:36:47 UTC, Paul Backus wrote:

 On Tuesday, 19 January 2021 at 22:34:04 UTC, Tim wrote:

 On Tuesday, 19 January 2021 at 22:31:47 UTC, Paul Backus 
 wrote:

 You've almost got it. The correct syntax is `is(T == U[], 
 U)`. You can read it as "there exists some type U such that 
 T == U[]".


 Thanks! Do I need to specify U in the template function?


 No, only inside the is(...) expression.


 What if it is a static array i.e. double[3]?


is(T == U[n], U, size_t n)
Jan 19 2021
parent Tim <tim.oliver tutanota.com> writes:
On Tuesday, 19 January 2021 at 22:45:19 UTC, Paul Backus wrote:

 On Tuesday, 19 January 2021 at 22:38:41 UTC, Tim wrote:

 On Tuesday, 19 January 2021 at 22:36:47 UTC, Paul Backus wrote:

 On Tuesday, 19 January 2021 at 22:34:04 UTC, Tim wrote:

 On Tuesday, 19 January 2021 at 22:31:47 UTC, Paul Backus 
 wrote:

 You've almost got it. The correct syntax is `is(T == U[], 
 U)`. You can read it as "there exists some type U such that 
 T == U[]".


 Thanks! Do I need to specify U in the template function?


 No, only inside the is(...) expression.


 What if it is a static array i.e. double[3]?


 is(T == U[n], U, size_t n)


Easy, thanks a lot!
Jan 19 2021