Working through the GNU smalltalk user's manual; noticed a slight error!

Good morning,

First of all, thanks for having this resource available. I'm greatly
enjoying learning Smalltalk, and being a vim-and-emacs person, being able
to tinker with this through the command-line has been great. I do wish I
could've gotten the gst-browser to work, but it appears quite allergic to
my mac (high sierra blah blah blah), and toying with Fink for some time was
not the saving grace I hoped it'd be. Drats.

Anyway. The reason why I'm emailing is about
https://www.gnu.org/software/smalltalk/manual/html_node/Invoking-code-blocks.html#Invoking-code-blocks
; specifically, the #checksOver:do: code block. It appears to be missing an
opening bracket (and also a closing one) after the method name, on line 2!

```

   Checking extend [
       checksOver: amount do: aBlock [
           history keysAndValuesDo: [:key :value |
               (value > amount)
                      ifTrue: [aBlock value: key]
           ]

       ]
   ]

```

...would be the correction.

I know this is really trivial, but it's a thing I noticed and that tripped
me up. Everything else has worked out of the box, as it were.

No obligation to fix this; I'm not sure if the manual is maintained, but
I've appreciated going through it so much, I felt an obligation to give
some tiny thanks back, if only in the form of syntax-checking, lol.

Take care!
-