string mixin and alias

2016-07-28 Thread Andre Pany via Digitalmars-d-learn 

Hi,

is there a way to alias a string mixin?
Neither foo nor foo2 compiles.

import std.meta : Alias;
alias foo = (s) => Alias!(mixin(generateCode(s)));
alias foo2(string s) = Alias!(mixin(generateCode(s)));

string generateCode(string s){return "";}

void main()
{
  enum s = "a = 2 + 3; b = 4 + a;";
  foo(s);
  foo2(s);
}

Kind regards
André

Re: string mixin and alias

2016-07-28 Thread rikki cattermole via Digitalmars-d-learn 

On 29/07/2016 6:38 PM, Andre Pany wrote:

Hi,

is there a way to alias a string mixin?
Neither foo nor foo2 compiles.

import std.meta : Alias;
alias foo = (s) => Alias!(mixin(generateCode(s)));
alias foo2(string s) = Alias!(mixin(generateCode(s)));

string generateCode(string s){return "";}

void main()
{
  enum s = "a = 2 + 3; b = 4 + a;";
  foo(s);
  foo2(s);
}

Kind regards
André


Well those string mixins are not evaluating out to a symbol. So that 
could be a rather big problem for the Alias template.

Re: string mixin and alias

2016-07-29 Thread pineapple via Digitalmars-d-learn 

On Friday, 29 July 2016 at 06:38:17 UTC, Andre Pany wrote:

Hi,

is there a way to alias a string mixin?
Neither foo nor foo2 compiles.

import std.meta : Alias;
alias foo = (s) => Alias!(mixin(generateCode(s)));
alias foo2(string s) = Alias!(mixin(generateCode(s)));

string generateCode(string s){return "";}

void main()
{
  enum s = "a = 2 + 3; b = 4 + a;";
  foo(s);
  foo2(s);
}

Kind regards
André


It's not clear what you're trying to accomplish. What would you 
expect this code to do?

Re: string mixin and alias

2016-07-29 Thread Andre Pany via Digitalmars-d-learn 

On Friday, 29 July 2016 at 12:11:44 UTC, pineapple wrote:

On Friday, 29 July 2016 at 06:38:17 UTC, Andre Pany wrote:

Hi,

is there a way to alias a string mixin?
Neither foo nor foo2 compiles.

import std.meta : Alias;
alias foo = (s) => Alias!(mixin(generateCode(s)));
alias foo2(string s) = Alias!(mixin(generateCode(s)));

string generateCode(string s){return "";}

void main()
{
  enum s = "a = 2 + 3; b = 4 + a;";
  foo(s);
  foo2(s);
}

Kind regards
André


It's not clear what you're trying to accomplish. What would you 
expect this code to do?


It is more or less syntax sugar. In the main function instead
of writing "mixin(generateCode(s));" I want to write "foo(s);".
So, the mixin statement is hidden while the functionality of 
mixin stays.


Kind regards
André

Re: string mixin and alias

2016-07-29 Thread Steven Schveighoffer via Digitalmars-d-learn 

On 7/29/16 2:38 AM, Andre Pany wrote:

Hi,

is there a way to alias a string mixin?
Neither foo nor foo2 compiles.

import std.meta : Alias;
alias foo = (s) => Alias!(mixin(generateCode(s)));


s is a runtime parameter. You can't mixin stuff that is only available 
at runtime.



alias foo2(string s) = Alias!(mixin(generateCode(s)));


This would work if the string is "main", let's say.


string generateCode(string s){return "";}

void main()
{
  enum s = "a = 2 + 3; b = 4 + a;";


This does not result in a symbol, an alias needs a symbol.

-Steve

Re: string mixin and alias

2016-07-29 Thread pineapple via Digitalmars-d-learn 

On Friday, 29 July 2016 at 12:22:54 UTC, Andre Pany wrote:

It is more or less syntax sugar. In the main function instead
of writing "mixin(generateCode(s));" I want to write "foo(s);".
So, the mixin statement is hidden while the functionality of 
mixin stays.


Kind regards
André



As far as I know, there's no way to hide away the `mixin` 
statement in a template or alias. You could do something like 
this, if you really wanted to, but really the only difference is 
that it uses fewer parentheses.


string generateCode(string s){return "";}
enum foo(string s) = generateCode(s);

void main(){
enum s = "int a = 2 + 3; int b = 4 + a;";
mixin foo!s;
}

Re: string mixin and alias

2016-07-29 Thread Jesse Phillips via Digitalmars-d-learn 
D won't let you hide the mixin, the keyword is there specifically 
to indicate code is being injected in that location.


This isn't what you are looking for, but you can do something 
like this:


-
string generateCode(string s){return "";}

void main()
{
enum s = "a = 2 + 3; b = 4 + a;";
foo!(s);
}

void foo(alias s)() {
mixin(generateCode(s));
}
-

Here the generateCode() is mixed in to the context of foo(), 
which is fine if your code is performing actions but is no good 
if you're creating declarations that you want to use in the 
context of main().

Re: string mixin and alias

2016-07-29 Thread Jesse Phillips via Digitalmars-d-learn 

On Friday, 29 July 2016 at 18:34:56 UTC, Jesse Phillips wrote:
Here the generateCode() is mixed in to the context of foo(), 
which is fine if your code is performing actions but is no good 
if you're creating declarations that you want to use in the 
context of main().


Here is a fully functioning example:

---
string generateCode(string s){return s;}

void main()
{
int a, b;
enum s = "a = 2 + 3; b = 4 + a;";
foo!(s)(a, b);
assert(a == 5);
assert(b == 9);
}

void foo(alias s)(ref int a, ref int b) {
mixin(generateCode(s));
}
---

Re: string mixin and alias

2016-07-29 Thread Andre via Digitalmars-d-learn 

On Friday, 29 July 2016 at 18:39:23 UTC, Jesse Phillips wrote:

On Friday, 29 July 2016 at 18:34:56 UTC, Jesse Phillips wrote:
Here the generateCode() is mixed in to the context of foo(), 
which is fine if your code is performing actions but is no 
good if you're creating declarations that you want to use in 
the context of main().


Here is a fully functioning example:

---
string generateCode(string s){return s;}

void main()
{
int a, b;
enum s = "a = 2 + 3; b = 4 + a;";
foo!(s)(a, b);
assert(a == 5);
assert(b == 9);
}

void foo(alias s)(ref int a, ref int b) {
mixin(generateCode(s));
}
---


Thanks for all the answers.

Kind regards
Andre