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digitalmars.D.learn - static variable A cannot be read at compile time

reply Newbie2019 <newbie2019 gmail.com> writes:
https://run.dlang.io/is/s4cfiv

onlineapp.d(23): Error: static variable A cannot be read at 
compile time
onlineapp.d(23): Error: cannot implicitly convert expression 1 of 
type int to int*

I see no reason the code should not work,  and the second error 
message make no sense.

please suggestion how should I made this code to work.
Jun 12 2019
parent reply "H. S. Teoh" <hsteoh quickfur.ath.cx> writes:
On Wed, Jun 12, 2019 at 01:12:58PM +0000, Newbie2019 via Digitalmars-d-learn
wrote:

 https://run.dlang.io/is/s4cfiv
 
 onlineapp.d(23): Error: static variable A cannot be read at compile time
 onlineapp.d(23): Error: cannot implicitly convert expression 1 of type int
 to int*
 
 I see no reason the code should not work,  and the second error message make
 no sense.


Read: https://wiki.dlang.org/User:Quickfur/Compile-time_vs._compile-time


T

-- 
A mathematician is a device for turning coffee into theorems. -- P. Erdos
Jun 12 2019
parent reply Newbie2019 <newbie2019 gmail.com> writes:
On Wednesday, 12 June 2019 at 13:53:09 UTC, H. S. Teoh wrote:

 On Wed, Jun 12, 2019 at 01:12:58PM +0000, Newbie2019 via 
 Digitalmars-d-learn wrote:
 Read: 
 https://wiki.dlang.org/User:Quickfur/Compile-time_vs._compile-time


 T



Thanks for the tips.

I move the static array into local var then it work.

Still the last error message make no sense here.
Jun 12 2019
parent Machine Code <jckj33 gmail.com> writes:
On Wednesday, 12 June 2019 at 14:09:08 UTC, Newbie2019 wrote:

 On Wednesday, 12 June 2019 at 13:53:09 UTC, H. S. Teoh wrote:

 On Wed, Jun 12, 2019 at 01:12:58PM +0000, Newbie2019 via 
 Digitalmars-d-learn wrote:
 Read: 
 https://wiki.dlang.org/User:Quickfur/Compile-time_vs._compile-time


 T



 Thanks for the tips.

 I move the static array into local var then it work.


You keep a static variable then initilizae it at module's static 
this() { },

something like this:


struct Arguments {
         int     verbose;
}
__gshared Arguments A;

__gshared option[1] long_options;

static this()
{
      long_options =  [option(cast(char*)("verbose".ptr), 
no_argument,  &A.verbose, 1)];
}



 Still the last error message make no sense here.


It's the call to struct constructor that you're missing. Those 
C-style array initialziation doesn't work with D (as far I know) 
so that you have to explicit (and I like it, even if C-style did 
work in D, I wouldn't use) so you have to call the constructor as 
I did in below code. Anothing type error is: "verbose" is of D's 
string type, not a raw pointer as in C and you need in your 
struct member. To get that, use D's .ptr property then cast away 
immutable to get the const char* you need.

I guess you're implementing a command-line parsing? if you aren't 
aware of, D has something in its standard library for that: 
https://dlang.org/phobos/std_getopt.html might be helpful.

That being said, if you find tedious to build an array with 
default values for specific struct members, you can automate all 
that with D CTFE or just use derived struct with default members. 
Things here do not need to be like C at high-level :)
Jun 12 2019