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Why are preprocessor macros evil and what are the alternatives?
...can't be debugged.
When you have a macro that translates to a number or a string, the source code will have the macro name, and many debuggers, you can't "see" what the macro translates to. So you don't actually know what is going on.
Replacement: Use enum or const T
For "function-like" macros,...
How to combine paths in Java?
...
Rather than keeping everything string-based, you should use a class which is designed to represent a file system path.
If you're using Java 7 or Java 8, you should strongly consider using java.nio.file.Path; Path.resolve can be used to combine one path wi...
How does HTTP file upload work?
... here ...
------WebKitFormBoundaryePkpFF7tjBAqx29L--
NOTE: each boundary string must be prefixed with an extra --, just like in the end of the last boundary string. The example above already includes this, but it can be easy to miss. See comment by @Andreas below.
Instead of URL encoding the form...
How to import multiple .csv files at once?
...t;-
list.files(pattern = "*.csv") %>%
map_df(~fread(.))
The stringsAsFactors = FALSE argument keeps the dataframe factor free, (and as marbel points out, is the default setting for fread)
If the typecasting is being cheeky, you can force all the columns to be as characters with the c...
Uses for Optional
...de to work, but it's rather clumsy. Suppose you have a method that takes a string followed by an optional second string. Accepting an Optional as the second arg would result in code like this:
foo("bar", Optional.of("baz"));
foo("bar", Optional.empty());
Even accepting null is nicer:
foo("bar", ...
Rails: How can I set default values in ActiveRecord?
... Rails 3.2+ - for earlier, use self.attributes.has_key?, and you need to a string instead of a symbol.
– Cliff Darling
Oct 22 '12 at 15:54
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Comparing Dates in Oracle SQL
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31-DEC-95 isn't a string, nor is 20-JUN-94. They're numbers with some extra stuff added on the end. This should be '31-DEC-95' or '20-JUN-94' - note the single quote, '. This will enable you to do a string comparison.
However, you're not doin...
SQL SELECT speed int vs varchar
...2147483648 to +2147483647 )
character types occupy 4 bytes plus the actual strings.
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A gentle tutorial to Emacs/Swank/Paredit for Clojure
... ((candidates
(remove-if-not
(lambda (jar)
(string-match-p "clojure\\([0-9.-]+\\(SNAPSHOT|MASTER\\)?\\)?\\.jar$" jar))
jars)))
(if candidates
(car candidates)
(expand-file-name "~/.clojure/clojure.jar"))))
(defun find-clojure-contrib-jar (j...
MongoDB SELECT COUNT GROUP BY
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I need some extra operation based on the result of aggregate function. Finally I've found some solution for aggregate function and the operation based on the result in MongoDB. I've a collection Request with field request, source, status...