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(emacs-lisp-intro.info)Second Buffer Related Review

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Enter node , (file) or (file)node

Review
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   Here is a brief summary of some of the topics covered in this
chapter.

`or'
     Evaluate each argument in sequence, and return the value of the
     first argument that is not `nil'; if none return a value that is
     not `nil', return `nil'.  In brief, return the first true value of
     the arguments; return a true value if one _or_ any of the other
     are true.

`and'
     Evaluate each argument in sequence, and if any are `nil', return
     `nil'; if none are `nil', return the value of the last argument.
     In brief, return a true value only if all the arguments are true;
     return a true value if one _and_ each of the others is true.

`&optional'
     A keyword used to indicate that an argument to a function
     definition is optional; this means that the function can be
     evaluated without the argument, if desired.

`prefix-numeric-value'
     Convert the `raw prefix argument' produced by `(interactive "P")'
     to a numeric value.

`forward-line'
     Move point forward to the beginning of the next line, or if the
     argument is greater than one, forward that many lines.  If it
     can't move as far forward as it is supposed to, `forward-line'
     goes forward as far as it can and then returns a count of the
     number of additional lines it was supposed to move but couldn't.

`erase-buffer'
     Delete the entire contents of the current buffer.

`bufferp'
     Return `t' if its argument is a buffer; otherwise return `nil'.