Compile time regex matching

[Artur Skawina via Digitalmars-d-learn]

On 07/14/14 13:42, Philippe Sigaud via Digitalmars-d-learn wrote:
> asserts get an entire copy of the parse tree. It's a bit wasteful, but
> using 'immutable' directly does not work here, but this is OK:
> 
>     enum res = MyRegex("abcabcdefFOOBAR"); // compile-time parsing
>     immutable result = res; // to avoid copying the enum value everywhere   
 
   static immutable result = MyRegex("abcabcdefFOOBAR"); // compile-time parsing


> The static asserts then works (not the toString, though). Maybe

diff --git a/pegged/peg.d b/pegged/peg.d
index 98959294c40e..307e8a14b1dd 100644
--- a/pegged/peg.d
+++ b/pegged/peg.d
@@ -55,7 +55,7 @@ struct ParseTree
     /**
     Basic toString for easy pretty-printing.
     */
-    string toString(string tabs = "")
+    string toString(string tabs = "") const
     {
         string result = name;
 
@@ -262,7 +262,7 @@ Position position(string s)
 /**
 Same as previous overload, but from the begin of P.input to p.end
 */
-Position position(ParseTree p)
+Position position(const ParseTree p)
 {
     return position(p.input[0..p.end]);
 }

[completely untested; just did a git clone and fixed the two
 errors the compiler was whining about. Hmm, did pegged get
 faster? Last time i tried (years ago) it was unusably slow;
 right now, compiling your example, i didn't notice the extra
 multi-second delay that was there then.]

artur