How should I include code samples in posts?

Question

What are best practices for including sections of Mathematica code in posts?

Mathematica differs from many programming languages because many of us use it in "REPL" (read-evaluate-print-line) mode, so output is interspersed with input, making it hard to copy and paste code. Are there any tricks to ameliorate this?

Answer 1

Copying output from Mathematica can be tricky at times. Here are some tips on making it easier:

Copying:

• Use Copy As -> Plain Text, or Copy As -> Input Text from the context menu to avoid copying (not really human readable) box expressions.

• If you copy only input cells, the In/Out labels will not be copied. To select all input cells in a notebook, Alt-Click an input cell bracket. (You can copy the relevant section to a new notebook before selecting input cells.)

• Whenever possible, make sure that the code posted can be copied back to Mathematica and evaluated. But in some special cases it's good to show the formatted expression too, as a screenshot. The image uploader palette makes this very easy.

Unfortunately formatting (indentation and newlines) will get lost when the code is copied. I do not know if there's a good solution for this (I'd be very interested!)

Pasting:

• When pasting back code to Mathematica, it'll get pasted into a single cell. Cell ->Divide Cell (CTRL-SHIFT-D) is a convenient way to break it into parts again.

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A note about In/Out labels:

When I post code to be copied as a whole, I always avoid In/Out labels, as this is inconvenient. But when I'm showing the process of doing something, together with the output, and commenting on each step, I prefer to keep In/Out labels to make it very clear what is the input and what is the output.

Answer 2

I usually edit away any In/Out labels that may be left during copying. I then comment out the output

So

In[108]:= D[Cos[x] Exp[x], x]

Out[108]= E^x Cos[x] - E^x Sin[x]

becomes:

D[Cos[x] Exp[x], x]

(*  
===> E^x Cos[x] - E^x Sin[x]
*)

Answer 3

I have taken to using a combination of QUOTE and CODE blocks. That is > followed by five spaces before each line. It's quick to type by hand, and I think it both visually and logically carries the meaning of output.

Range@9

{1, 2, 3, 4, 5, 6, 7, 8, 9}

Answer 4

I find Sjoerd's way of presenting code a bit bloated.

Why not simply use >> for input and << for output?

>> (*If comments are part of the pasted code, there will be no confusion*)
   Print["as to what's a comment and what's code (not that it was such a big problem...)"];

<< "as to what's a comment and what's code (not that it was such a big problem...)"

Because the code block is not executable, since << and >> are Mathematica functions.