#

##
2.4.8.3 Sharpsign Left-Parenthesis

`#(` and `)` are used to notate a *simple vector*.

If an unsigned decimal integer appears between the `#` and `(`, it specifies explicitly the length of the *vector*. The consequences are undefined if the number of *objects* specified before the closing `)` exceeds the unsigned decimal integer. If the number of *objects* supplied before the closing `)` is less than the unsigned decimal integer but greater than zero, the last *object* is used to fill all remaining elements of the *vector*. The consequences are undefined if the unsigned decimal integer is non-zero and number of *objects* supplied before the closing `)` is zero. For example,

#(a b c c c c)
#6(a b c c c c)
#6(a b c)
#6(a b c c)

all mean the same thing: a *vector* of length `6` with *elements* `a`, `b`, and four occurrences of `c`. Other examples follow:

#(a b c) ;A vector of length 3
#(2 3 5 7 11 13 17 19 23 29 31 37 41 43 47)
;A vector containing the primes below 50
#() ;An empty vector

The notation `#()` denotes an empty *vector*, as does `#0()`.
For information on how the *Lisp printer* prints *vectors*, see Section 22.1.3.4 (Printing Strings), Section 22.1.3.6 (Printing Bit Vectors), or Section 22.1.3.7 (Printing Other Vectors).

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