Re: [julia-users] Swapping two columns (or rows) of an array efficiently

[Steven G. Johnson]

As a general rule, with Julia one needs to unlearn the instinct (from 
Matlab or Python) that "efficiency == clever use of library functions", 
which turns all optimization questions into "is there a built-in function 
for X" (and if the answer is "no" you are out of luck).   Loops are fast, 
and you can easily beat general-purpose library functions with your own 
special-purpose code.