| (...) | (expressions) or (lists) live in parentheses |
| 'symbol | what is a symbol? It's just an object with a name. |
| variable | variables are not surrounded by anything |
| ?C | represents character C |
| ?\\ | escape sequence for backslash \ |
| "string" | strings are enclosed in double-quotes |
| `... | ??? |
| (a . b) | a cons cell with CAR=a and CDR=b (see manual) |
| ((a . v1) (b . v2)) | association list ("alist"); a, b are the keys and v* the values |
| [el1 el2 el3] | a vector of three elements el1, el2, el3 (always one-dimensional) |
To compare a variable with a string, use something like this:
(string= window-system "x") (string= window-system nil)
string= is the function for string comparison,
window-system is a variable containing information about the
windowing environment of the running emacs and "x" is a string,
nil is a constant symbol with the value nil (-- "a symbol with the
name `nil'; it is the logical truth value false; and it is the empty
list--the list of zero elements. When used as a variable, nil
always has the value nil"). In the example above, nil and "nil"
could have been used;