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Can someone explain the traverse function in Haskell?
...an also compare it to Foldable, which defines the related function traverse_.
traverse_ :: (Foldable t, Applicative f) => (a -> f b) -> t a -> f ()
So you can see that the key difference between Foldable and Traversable is that the latter allows you to preserve the shape of the struct...
Is it possible to install another version of Python to Virtualenv?
...igure --prefix=/home/<user>/.localpython in fact make clean returned error. 2. virtualenv name -p=/python/path didn't worked instead virtualenv name -p /python/path did worked. I assume it's down to virtualenv version. cheers!
– zzart
Mar 26 '12 at 12:37...
Will using 'var' affect performance?
...e it can't figure out what type you intended to use, you'll get a compiler error.
The only trick is that var will infer an exact type where you may have chosen an Interface or parent type if you were to set the type manually.
Update 8 Years Later
I need to update this as my understanding has change...
How to compare two floating point numbers in Bash?
...questions/8654051/… e.g. $ echo "1.1+2e+02" | bc (standard_in) 1: syntax error
– Nemo
Feb 2 '16 at 10:55
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Run cron job only if it isn't already running
...on job as a sort of watchdog for a daemon that I've created. If the daemon errors out and fails, I want the cron job to periodically restart it... I'm not sure how possible this is, but I read through a couple of cron tutorials and couldn't find anything that would do what I'm looking for...
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Converting Dictionary to List? [duplicate]
...ied to access the list resulting from dictlist=dict.items(), I then got an error trying to access it like a list: dictlist[i][1]. Python3 doc says: ~~~~ "The objects returned by dict.keys(), dict.values() and dict.items() are view objects. They provide a dynamic view on the dictionary’s entries, ...
How can I start PostgreSQL server on Mac OS X?
...t is the result of pg_ctl -D /usr/local/var/postgres status?
Are there any error messages in the server.log?
Make sure tcp localhost connections are enabled in pg_hba.conf:
# IPv4 local connections:
host all all 127.0.0.1/32 trust
Check the listen_addresses and port in postgresql.conf:
...
Cron and virtualenv
...ll
It's tricky to spot why this fails as /var/log/syslog doesn't log the error details. Best to alias yourself to root so you get emailed with any cron errors. Simply add yourself to /etc/aliases and run sendmail -bi.
More info here:
http://codeinthehole.com/archives/43-Running-django-cronjobs-...
List comprehension on a nested list?
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answered Aug 6 '13 at 6:05
Andrew ClarkAndrew Clark
171k2525 gold badges236236 silver badges278278 bronze badges
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‘ld: warning: directory not found for option’
... this:
Click on your project (targets)
Click on Build Settings
if your error includes the -L flag, then delete the values in Library Search Paths
if your error includes the -F flag, then delete the values in Framework Search Paths
And regarding the second error, sorry i can't help you out w...