haskell - Compiler switch to turn debugging messages on/off? -


ok, here's simple question. i've written function debug :: string -> io (). i'd set things when compile program 1 way, function writes standard error, , if compile program way, function becomes no-op. there easy compile-time switch that? or have implement myself?

i don't think involving trace right approach solve problem.

instead, use preprocessor disable/enable debug messages. put following in separate file:

{-# language cpp #-} import system.io  debug :: string -> io () debug message = #ifdef debug   hputstrln stderr message #else   return () #endif

the {-# language cpp #-} line enables c preprocessor current file. can compile file with/without debugging using ghc -ddebug or ghc.


Comments

Post a Comment

Popular posts from this blog

.htaccess - First slash is removed after domain when entering a webpage in the browser -

sometimes when hit address of webpage in browser, removes first slash after domain. examples: www.mywebsite.com/scripts/script_6.php -> trying load www.mywebsite.comscripts/script_6.php www.mywebsite.com/test.php -> trying load www.mywebsite.comtest.php after entering again, loads page. a .htaccess settings must wrong: rewritebase / errordocument 404 http://www.mywebsite.com/oops.php errordocument 401 /notallowed.php rewriteengine on # turn on rewriting engine #gzip <ifmodule mod_deflate.c> addoutputfilterbytype deflate text/text text/html text/plain text/xml text/css application/x- javascript application/javascript </ifmodule> #end gzip rewritecond %{http_host} ^mywebsite\.com rewriterule ^(.*)$ http://www.mywebsite.com$1 [r=permanent,l] directoryindex index6.php rewriterule ^termsofuse/?$ termsofuse.php [nc,l] # handle requests "adpolicy" rewriterule ^privacy-policy/?$ privacy-policy.php [nc,l] # handle requ...
Read more

Socket.connect doesn't throw exception in Android -

if put nonsense url no exception thrown , none of rest of code executed not rest of asynctask called method connects. try { socketcliente.connect(new inetsocketaddress("f", port), 2000); } catch (unknownhostexception e) { geterror("host doesn't exist"); return -1; } catch (ioexception e) { geterror("could not connect: host down"); return -1; } add catch statement. catch ( exception e ) { log.d(tag, e.getmessage(),e); toast.maketext(getapplicationcontext(), "unexpected error:" + e.getmessage(), toast.length_long).show(); } this write log , pop toast tell what's going on.
Read more

SPSS keyboard combination alters encoding -

my question not have programming practical issue on spss. accident keyword combination cannot remember because did not intend press changed encoding in spss , text in data in different language english shown small boxes. nevertheless, when kind of analysis performed different language text shown in output. does know reason? tried change encoding did not produce result. first, @ edit > options , see whether setting unicode or locale. might fix it. if have text in multiple languages, want unicode. otherwise, may have specific locale set wrong. can change set locale, need know locale want use.
Read more