This section describes the Lisp functions and variables that pertain to reading.
In the functions below, stream stands for an input stream (see
the previous section). If stream is
nil or omitted, it
defaults to the value of
end-of-file error is signaled if reading encounters an
unterminated list, vector, or string.
This function reads one textual Lisp expression from stream, returning it as a Lisp object. This is the basic Lisp input function.
This function reads the first textual Lisp expression from the text in string. It returns a cons cell whose car is that expression, and whose cdr is an integer giving the position of the next remaining character in the string (i.e., the first one not read).
If start is supplied, then reading begins at index start in the string (where the first character is at index 0). If you specify end, then reading is forced to stop just before that index, as if the rest of the string were not there.
For example:(read-from-string "(setq x 55) (setq y 5)") ⇒ ((setq x 55) . 11) (read-from-string "\"A short string\"") ⇒ ("A short string" . 16) ;; Read starting at the first character. (read-from-string "(list 112)" 0) ⇒ ((list 112) . 10) ;; Read starting at the second character. (read-from-string "(list 112)" 1) ⇒ (list . 5) ;; Read starting at the seventh character, ;; and stopping at the ninth. (read-from-string "(list 112)" 6 8) ⇒ (11 . 8)
This variable holds the default input stream—the stream that
readuses when the stream argument is
nil. The default is
t, meaning use the minibuffer.
nil, this variable enables the reading of circular and shared structures. See Circular Objects. Its default value is