17.1 Sequence Concepts

A sequence is an ordered collection of elements, implemented as either a vector or a list.

Sequences can be created by the function make-sequence, as well as other functions that create objects of types that are subtypes of sequence (e.g., list, make-list, mapcar, and vector).

A sequence function is a function defined by this specification or added as an extension by the implementation that operates on one or more sequences. Whenever a sequence function must construct and return a new vector, it always returns a simple vector. Similarly, any strings constructed will be simple strings.

concatenate        length              remove             
copy-seq           map                 remove-duplicates  
count              map-into            remove-if          
count-if           merge               remove-if-not      
count-if-not       mismatch            replace            
delete             notany              reverse            
delete-duplicates  notevery            search             
delete-if          nreverse            some               
delete-if-not      nsubstitute         sort               
elt                nsubstitute-if      stable-sort        
every              nsubstitute-if-not  subseq             
fill               position            substitute         
find               position-if         substitute-if      
find-if            position-if-not     substitute-if-not  
find-if-not        reduce                                 

Figure 17-1. Standardized Sequence Functions

17.1.1 General Restrictions on Parameters that must be Sequences