• N.S. (14/14) Sep 05 2020 I'd like to check whether a variable is initialized or not. And
• Steven Schveighoffer (7/24) Sep 05 2020 When you set the initial value of x to void, it means "don't do
• N.S. (4/30) Sep 05 2020 Do I have to create additional variable bool x_is_valid? Problem
• starcanopy (17/31) Sep 05 2020 You might consider Nullable from std.typecons; however, if you're
• N.S. (2/36) Sep 05 2020 Perfect, thanks!

N.S. <ns null.com> writes:

I'd like to check whether a variable is initialized or not. And 
I'd also like to uninitialize a variable that is already 
initialized. Thanks!

int x = void;

if (x == void)
{
     writeln("x not initialized");
}
else
{
     // OK, use x
}

// Uninitialize x
x = void;

Steven Schveighoffer <schveiguy gmail.com> writes:

On 9/5/20 11:42 PM, N.S. wrote:
 I'd like to check whether a variable is initialized or not. And I'd also 
 like to uninitialize a variable that is already initialized. Thanks!
 
 int x = void;
 
 if (x == void)

There isn't a way to check this.

 {
      writeln("x not initialized");
 }
 else
 {
      // OK, use x
 }
 
 // Uninitialize x
 x = void;
 

When you set the initial value of x to void, it means "don't do 
anything, let whatever data is already on the stack be the value of x".

So "uninitialize" doesn't really mean anything. It would technically 
mean "do nothing".

-Steve

N.S. <ns null.com> writes:

On Sunday, 6 September 2020 at 03:56:51 UTC, Steven Schveighoffer 
wrote:
 On 9/5/20 11:42 PM, N.S. wrote:
 I'd like to check whether a variable is initialized or not. 
 And I'd also like to uninitialize a variable that is already 
 initialized. Thanks!
 
 int x = void;
 
 if (x == void)

 There isn't a way to check this.

 {
      writeln("x not initialized");
 }
 else
 {
      // OK, use x
 }
 
 // Uninitialize x
 x = void;
 

 When you set the initial value of x to void, it means "don't do 
 anything, let whatever data is already on the stack be the 
 value of x".

 So "uninitialize" doesn't really mean anything. It would 
 technically mean "do nothing".

 -Steve

Do I have to create additional variable bool x_is_valid? Problem 
is I got many variables. Thanks.

starcanopy <starcanopy protonmail.com> writes:

On Sunday, 6 September 2020 at 03:42:36 UTC, N.S. wrote:
 I'd like to check whether a variable is initialized or not. And 
 I'd also like to uninitialize a variable that is already 
 initialized. Thanks!

 int x = void;

 if (x == void)
 {
     writeln("x not initialized");
 }
 else
 {
     // OK, use x
 }

 // Uninitialize x
 x = void;

You might consider Nullable from std.typecons; however, if you're 
avoiding implicit initialization for performance reasons, then 
this solution might not be applicable.

import std.stdio: writeln;
import std.typecons: Nullable;

Nullable!int x;

if (x.isNull)
{
	writeln("x not 'initialized'");
}
else
{
	// OK, use x
}

// 'Uninitialize' x
x.nullify();

N.S. <ns null.com> writes:

On Sunday, 6 September 2020 at 05:06:26 UTC, starcanopy wrote:
 On Sunday, 6 September 2020 at 03:42:36 UTC, N.S. wrote:
 I'd like to check whether a variable is initialized or not. 
 And I'd also like to uninitialize a variable that is already 
 initialized. Thanks!

 int x = void;

 if (x == void)
 {
     writeln("x not initialized");
 }
 else
 {
     // OK, use x
 }

 // Uninitialize x
 x = void;

 You might consider Nullable from std.typecons; however, if 
 you're avoiding implicit initialization for performance 
 reasons, then this solution might not be applicable.

 import std.stdio: writeln;
 import std.typecons: Nullable;

 Nullable!int x;

 if (x.isNull)
 {
 	writeln("x not 'initialized'");
 }
 else
 {
 	// OK, use x
 }

 // 'Uninitialize' x
 x.nullify();

Perfect, thanks!