Debug help - foreach opApply overload School example: Programming in D

[Dejan Lekic]

On Monday, 18 August 2025 at 13:32:57 UTC, Brother Bill wrote:
> Page 496 of Programming in D
>
> Going in circles.  Please correct so it compiles and works.
> An explanation would be helpful also.

Ali's book have a section about const member qualifier - "51.5 
const member functions", but I think it should have more examples 
for absolute beginners. The online D reference has a better 
example here: 
https://dlang.org/spec/declaration.html#methods-returning-qualified . This example shows what happens when method is declared const (see how struct member gets const qualifier). Pay attention to the comment `// error, cannot convert const(int)* to int*` . This is exactly why you have the similar error. if Ali's reading this - it would be good to include an example showing this problem. To be fair, his book does not have this exact code - it was written by you.

So, to fix your error, you can remove the "const" method 
qualifier from opApply, or cast the const away from the member 
when you use it.