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What makes Lisp macros so special?
Reading Paul Graham's essays on programming languages one would think that Lisp macros are the only way to go. As a busy developer, working on other platforms, I have not had the privilege of using Lisp macros. As someone who wants to understand the buzz, please explain what makes this feature s...
Find a Git branch containing changes to a given file
...)
FILENAME="<filename>"
git log --all --format=%H $FILENAME | while read f; do git branch --contains $f; done | sort -u
Manually inspect:
gitk --all --date-order -- $FILENAME
Find all changes to FILENAME not merged to master:
git for-each-ref --format="%(refname:short)" refs/heads | gre...
Python: fastest way to create a list of n lists
...r more formal and can be extended in a variety of situations, after having read a dataset.
Method 1: Conceptual
X2=[]
X1=[1,2,3]
X2.append(X1)
X3=[4,5,6]
X2.append(X3)
X2 thus has [[1,2,3],[4,5,6]] ie a list of lists.
Method 2 : Formal and extensible
Another elegant way to store a list as a li...
Which is more efficient, a for-each loop, or an iterator?
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If you are just wandering over the collection to read all of the values, then there is no difference between using an iterator or the new for loop syntax, as the new syntax just uses the iterator underwater.
If however, you mean by loop the old "c-style" loop:
for(int i=0...
Using varchar(MAX) vs TEXT on SQL Server
I just read that the VARCHAR(MAX) datatype (which can store close to 2GB of char data) is the recommended replacement for the TEXT datatype in SQL Server 2005 and Next SQL SERVER versions.
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R: += (plus equals) and ++ (plus plus) equivalent from c++/c#/java, etc.?
... While immutability is a great/desirable property for objects (read: less bugs) I don't think immutability relates to the += question. In other languages += can be applied to immutable types (like strings in .net). The operation simply creates a new object and assigns the given variabl...
How do you divide each element in a list by an int?
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I know this is an old reply but for anyone still reading it: keep in mind that when using numpy.array you should specify the type for example numpy.array([10,20,30,40,50,60,70,80,90], dtype='f')for loat. Otherwise dividing by 3 would give you just 3 as the result instead of...
What is a Question Mark “?” and Colon “:” Operator Used for? [duplicate]
...ard term for them or where I can find more information on their use? I've read that they are similar to an 'if' 'else' statement.
...
Safely remove migration In Laravel
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If the migration has been run (read: migrated) then you should roll back your migration to clear the history from your database table. Once you're rolled back you should be able to safely delete your migration file and then proceed with migrating again.
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What is the best JavaScript code to create an img element
... in the above code, if the values weren't hard coded). It's also easier to read (from a JS perspective):
$('#container').append($('<img>', {
src : "/path/to/image.jpg",
width : 16,
height : 16,
alt : "Test Image",
title : "Test Image"
}));
...