On 8/21/17 3:29 AM, WhatMeForget wrote:
On Sunday, 20 August 2017 at 19:41:14 UTC, Ali Çehreli wrote:
On 08/20/2017 12:27 PM, WhatMeWorry wrote:
> // Mixins are for mixing in generated code into the
source code.
> // The mixed in code may be generated as a template
instance
> // or a string.
Yes, it means that the string must be legal D code.
> mixin(`writeln(` ~ `Hello` ~ `);` );
Yes, that's a D string but the string itself is not legal D code
because it would be mixing in the following:
writeln(Hello);
The problem is, there is no Hello defined in the program.
You need to make sure that Hello is a string itself:
writeln("Hello");
So, you need to use the following mixin:
mixin(`writeln(` ~ `"Hello"` ~ `);` );
Of course, why didn't I "see" that before. I should have slept on it and
tried again with fresh eyes. I'm keeping a "beginners journal" on code
generation. Maybe write a 101 introduction with lots of samples and
exercises.
When doing mixins, especially when the code to generate the mixin string
isn't a simple literal, a great thing to do is to use pragma(msg) to
show the actual string you are mixing in.
e.g.:
enum mixinstr = ...
pragma(msg, mixinstr);
mixin(mixinstr);
Often times, your error is obvious when you see it that way.
-Steve
