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Common programming mistakes for Clojure developers to avoid [closed]
What are some common mistakes made by Clojure developers, and how can we avoid them?
8 Answers
...
“for” vs “each” in Ruby
...r
end
is more idiomatic. While Ruby supports looping constructs like for and while, the block syntax is generally preferred.
Another subtle difference is that any variable you declare within a for loop will be available outside the loop, whereas those within an iterator block are effectively priv...
SQL UPDATE SET one column to be equal to a value in a related table referenced by a different column
...QuestionAnswers a
on q.AnswerID = a.AnswerID
where q.QuestionID is null -- and other conditions you might want
I recommend to check what the result set to update is before running the update (same query, just with a select):
select *
from QuestionTrackings q
inner join QuestionAnswers a
on q.Answ...
Find duplicate lines in a file and count how many time each line was duplicated?
...at should do the trick in O(n) * avg_line_len. Does anyone know such a commandline tool?
– Droggl
Nov 20 '13 at 17:27
...
What is a 'semantic predicate' in ANTLR?
...ng of at least
// one number, optionally followed by zero or more comma's and numbers
parse
: number (',' number)* EOF
;
// matches a number that is between 1 and 3 digits long
number
: Digit Digit Digit
| Digit Digit
| Digit
;
// matches a single digit
Digit
: '0'..'9'
;
//...
Shared-memory objects in multiprocessing
...r array), place that in shared memory, wrap it with multiprocessing.Array, and pass that to your functions. This answer shows how to do that.
If you want a writeable shared object, then you will need to wrap it with some kind of synchronization or locking. multiprocessing provides two methods of do...
In Ruby, is there an Array method that combines 'select' and 'map'?
...
I usually use map and compact together along with my selection criteria as a postfix if. compact gets rid of the nils.
jruby-1.5.0 > [1,1,1,2,3,4].map{|n| n*3 if n==1}
=> [3, 3, 3, nil, nil, nil]
jruby-1.5.0 > [1,1,1,2,3,4].m...
C/C++ line number
... of debugging purposes, can I get the line number in C /C++ compilers?
(standard way or specific ways for certain compilers)
...
Skip download if files exist in wget?
...
-nc doesn't prevent the sending of the HTTP request and subsequent downloading of the file. It just doesn't do anything after downloading the file if the file has already been fully retrieved. Is there anyway to prevent making the HTTP request if the file already exists? stack...
How to run a single test from a rails test suite?
...kefile will NOT get executed.
To run a single test, use the following command from your rails project's main directory:
ruby -I test test/unit/my_model_test.rb -n test_name
This runs a single test named "name", defined in the MyModelTest class in the specified file. The test_name is formed by t...