• Clayton (12/12) Jul 19 2015 Pardon me for trivial question, Am new to D.
• Rikki Cattermole (7/19) Jul 19 2015 static if is for compile time known constants.
• Adam D. Ruppe (10/11) Jul 19 2015 In D, you can run regular runtime code at compile time in a lot

"Clayton" <johnsjdsd gmail.com> writes:

Pardon me for trivial question, Am new to D.


Why would a statement as below fail to compile. The plan is to do 
some computation at compile-time hence considering the static-if 
statement which fails to compile. The regular  if-statement 
compiles but is not useful since it is a runtime construct.

The error message I get is :  Error: variable i cannot be read at 
compile time




foreach( i; 0..size-1){
		static if  ( i == -1 ){
			//Do something
		}

	}

Rikki Cattermole <alphaglosined gmail.com> writes:

On 20/07/2015 12:17 a.m., Clayton wrote:
 Pardon me for trivial question, Am new to D.


 Why would a statement as below fail to compile. The plan is to do some
 computation at compile-time hence considering the static-if statement
 which fails to compile. The regular  if-statement compiles but is not
 useful since it is a runtime construct.

 The error message I get is :  Error: variable i cannot be read at
 compile time




 foreach( i; 0..size-1){
          static if  ( i == -1 ){
              //Do something
          }

      }

static if is for compile time known constants.
if is for runtime variables.

In this case it would be a runtime variable even if it is known at 
compile time.
Known at compile time != run at compile time. They overlap yes, just not 
the same thing.

"Adam D. Ruppe" <destructionator gmail.com> writes:

On Sunday, 19 July 2015 at 12:17:04 UTC, Clayton wrote:
 Pardon me for trivial question, Am new to D.

In D, you can run regular runtime code at compile time in a lot 
of cases. Just write an ordinary function that returns the data 
you need, then use it in a static variable initialization.

// example function, notice regular if and variables inside
int calculate(int i) { if(i < 0) return -i; else return i; }


static int value = calculate(5); // this is run at compile time



Ordinary functions will be interpreted if asked for their result 
in a context that only can be run at compile time, like a static 
variable initialization or inside a static if.