A <i>vector</i> is a structure that holds one or more elements in linear sequence. Vectors are enclosed by angle brackets ( <font face="Courier New">&lt; &gt;</font> ), with neighboring elements separated by a comma ( <font face="Courier New">,</font> ). Vector elements need not have uniform type: elements may mix between numbers, quotes, embedded vectors, and so on. The starting index for vectors is one ( <font face="Courier New">1</font> ), and the final index can be recovered by the <font face="Courier New">len( )</font> primitive.