• Bill Baxter <dnewsgroup billbaxter.com> Feb 06 2007
• Walter Bright <newshound digitalmars.com> Feb 06 2007
• BCS <BCS pathlink.com> Feb 06 2007
• Walter Bright <newshound digitalmars.com> Feb 06 2007
• Bradley Smith <user domain.invalid> Feb 06 2007

Bill Baxter <dnewsgroup billbaxter.com> writes:

Here's something fun that's now possible:

version(trace) {
     template Trace(char[] msg="") {
         const char[] Trace =
            `writefln("%s(%s): `~msg~`", __FILE__, __LINE__);`;
     }
} else {
     template Trace(char[] str="") {
         const char[] Trace = "";
     }
}

Zero overhead tracing when disabled, file and line number automatically 
supplied when enabled.

But just from trying to do this little thing, it's pretty clear to me 
that "my head asplode" if I have to write too much of this kinda thing 
without a better string literal syntax geared to this.

Something like:
       const char[] Trace =
"""
writefln("%s(%s):  (msg)", __FILE__, __LINE__);
"""
;

Would be much less likely to make me want to scratch my eyes out.


Also a little buglet --
You can call the above like
    mixin(Trace!("a_function"));
or
    mixin(Trace!());

But this doesn't work:
    mixin(Trace);

--bb

Walter Bright <newshound digitalmars.com> writes:

Bill Baxter wrote:
 Here's something fun that's now possible:
 
 version(trace) {
     template Trace(char[] msg="") {
         const char[] Trace =
            `writefln("%s(%s): `~msg~`", __FILE__, __LINE__);`;
     }
 } else {
     template Trace(char[] str="") {
         const char[] Trace = "";
     }
 }
 
 Zero overhead tracing when disabled, file and line number automatically 
 supplied when enabled.


Ah, I hadn't realize that this does solve the "point of instantiation" 
expansion with __FILE__ and __LINE__ <g>.

 
 But just from trying to do this little thing, it's pretty clear to me 
 that "my head asplode" if I have to write too much of this kinda thing 
 without a better string literal syntax geared to this.
 
 Something like:
       const char[] Trace =
 """
 writefln("%s(%s):  (msg)", __FILE__, __LINE__);
 """
 ;
 
 Would be much less likely to make me want to scratch my eyes out.


Yes, a better string literal syntax will probably have to be devised.

 Also a little buglet --
 You can call the above like
    mixin(Trace!("a_function"));
 or
    mixin(Trace!());
 
 But this doesn't work:
    mixin(Trace);


It's not a bug, it's as designed.

BCS <BCS pathlink.com> writes:

Bill Baxter wrote:
 Here's something fun that's now possible:
 
 version(trace) {
     template Trace(char[] msg="") {
         const char[] Trace =
            `writefln("%s(%s): `~msg~`", __FILE__, __LINE__);`;


i'd use

`writefln(__FILE__"("~itoa!(__LINE__)~"): %s), "`~msg~`");`;

file and line get folded and % dosn't mess thing up

COOL

Walter Bright <newshound digitalmars.com> writes:

BCS wrote:
 Bill Baxter wrote:
 Here's something fun that's now possible:

 version(trace) {
     template Trace(char[] msg="") {
         const char[] Trace =
            `writefln("%s(%s): `~msg~`", __FILE__, __LINE__);`;


 i'd use
 
 `writefln(__FILE__"("~itoa!(__LINE__)~"): %s), "`~msg~`");`;
 
 file and line get folded and % dosn't mess thing up
 
 COOL


or:

  const char[] Trace =
   std.metastrings.Format!(
        `writefln("%%s", "%s(%s): %s")`,
        __FILE__, __LINE__, msg
      );

Bradley Smith <user domain.invalid> writes:

Walter Bright wrote:
 BCS wrote:
 Bill Baxter wrote:
 Here's something fun that's now possible:

 version(trace) {
     template Trace(char[] msg="") {
         const char[] Trace =
            `writefln("%s(%s): `~msg~`", __FILE__, __LINE__);`;


 i'd use

 `writefln(__FILE__"("~itoa!(__LINE__)~"): %s), "`~msg~`");`;

 file and line get folded and % dosn't mess thing up

 COOL


 or:
 
  const char[] Trace =
   std.metastrings.Format!(
        `writefln("%%s", "%s(%s): %s")`,
        __FILE__, __LINE__, msg
      );


Typo. Missing ';' closing writefln statement. Should be the following.

  const char[] Trace =
   std.metastrings.Format!(
        `writefln("%%s", "%s(%s): %s");`,
        __FILE__, __LINE__, msg
      );