A vector is a fixed-length array of arbitrary values. Unlike a list, a vector supports constant-time access and update of its elements.
A vector prints similar to a list—as a parenthesized sequence of its elements—but a vector is prefixed with # after ', or it uses vector if one of its elements cannot be expressed with quote .
For a vector as an expression, an optional length can be supplied. Also, a vector as an expression implicitly quote s the forms for its content, which means that identifiers and parenthesized forms in a vector constant represent symbols and lists.
+Reading Vectors in The Racket Reference documents the fine points of the syntax of vectors.
> #("a" "b" "c")'#("a" "b" "c")
> #(name (that tune))'#(name (that tune))
> #4(baldwin bruce)'#(baldwin bruce bruce bruce)
"b"
'(that tune)
Like strings, a vector is either mutable or immutable, and vectors written directly as expressions are immutable.
Vectors can be converted to lists and vice versa via vector->list and list->vector ; such conversions are particularly useful in combination with predefined procedures on lists. When allocating extra lists seems too expensive, consider using looping forms like for/fold , which recognize vectors as well as lists.
'#("Three" "Blind" "Mice")
+Vectors in The Racket Reference provides more on vectors and vector procedures.