I've found 2 bugs in "Emacs Lisp Intro", which is
"An Introduction to Programming in Emacs Lisp"
by Bob Chassell.
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1st bug: When reading in Emacs in info and evaluating code
from Appendix C "A graph with labeled axes" with C-x C-e,
then switching to scratch buffer to print the graph, Emacs
complains about wrong number of arguments to a function
print-Y-axis .
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2nd bug: Appendix C "A graph with labeled axes" , function
print-X-axis-numbered-line does not print the first number
in the X axis of the graph.
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I've fixed both bugs and the fixed functions are in attached
file eintr-bugfix.el.gz
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Suggestion: Add another page with final versions of all
functions to print graph put together, so readers can
install them with C-x C-e, then switch to the scratch
buffer and print the graph. I've collected all the necessary
functions with bugfixes and a small extra function to make
it easier to print graph in attached file eintr-graph.el.gz
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Other:  At the end of Index node, when I press SPACE,
I'm taken to "C.2.1 Side Trip: Compute a Remainder"
instead of "About the Author" node.
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Earlier today I've sent a similar email, but got a response
about "mail not delivered". Trying to send it again.