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The Craft of Emacs

Types, errors and control flow

30 minutes

You sit back and admire M‑x xx.

There’s still much to be done for your cross stitch editor, but you’re proud of your little calculation. You’re keen to show it off, and what better place than the local cross stitch club?

At the following club meet, as everyone arranges their skeins, you nervously pull out your laptop and approach the club lead to enthuse over the glories of Emacs.

The club lead, a seasoned embroiderer, quickly masters the Emacs basics (keyboard shortcuts are a breeze compared to feather stitches) and moves on to to type the revered M‑x xx. She examines her own cross-stitch pattern, dilligently counting each stitch and thread, and inputs the figures with a few deft keystrokes.

No. strands? -5.8.  
No. stitches? Three thousand and fifty two.  

The club lead may be an embroiderer by night, but little did you know she’s a quality assurance tester by day. She hands back your laptop with a disapproving look.

Perplexed, you check the *xx* buffer.

Skeins
======
No. strands:
0
No. stitches:
0
No. skeins:
0
*xx*

There are some bugs to catch.