Deniz Dogan wrote:
I (too) often find myself writing code such as this:
if something
then putStrLn howdy there!
else if somethingElse
then putStrLn howdy ho!
else ...
I recall reading some tutorial about how you can use the Maybe monad
if your code starts looking like
Hello Andrew,
Sunday, June 21, 2009, 1:52:22 PM, you wrote:
d1x - doesDirectoryExist d1
if d1x
then do
f1x - doesFileExist (d1 / f1)
if f1x
then do
d2x - doesDirectoryExist d2
if d2x
then do
f2x - doesFileExist
On Jun 21, 2009, at 11:52 AM, Andrew Coppin wrote:
In a similar vein:
d1x - doesDirectoryExist d1
if d1x
then do
f1x - doesFileExist (d1 / f1)
if f1x
then do
d2x - doesDirectoryExist d2
if d2x
then do
f2x - doesFileExist (d2 / f2)
if
Sebastian Fischer wrote:
using Control.Monad.Error:
either (hPutStrLn stderr) return = runErrorT $
do d1x - lift $ doesDirectoryExist d1
unless d1x $ fail Directory ++ d1 ++ not found.
f1x - lift $ doesFileExist (d1 / f1)
unless f1x $ fail File ++ f1 ++ not found.
d2x
On Jun 21, 2009, at 2:36 PM, Sebastian Fischer wrote:
On Jun 21, 2009, at 11:52 AM, Andrew Coppin wrote:
...
When using
failUnless boolAction message = lift boolAction = (`unless`fail
message)
the code becomes
either (hPutStrLn stderr) return = runErrorT $
do failUnless
