6.6.9.3 List Constructors

This section describes the procedures for constructing new lists. list simply returns a list where the elements are the arguments, cons* is similar, but the last argument is stored in the cdr of the last pair of the list.

Scheme Procedure: list elem …

C Function: scm_list_1 (elem1)

C Function: scm_list_2 (elem1, elem2)

C Function: scm_list_3 (elem1, elem2, elem3)

C Function: scm_list_4 (elem1, elem2, elem3, elem4)

C Function: scm_list_5 (elem1, elem2, elem3, elem4, elem5)

C Function: scm_list_n (elem1, …, elemN, SCM_UNDEFINED)

Return a new list containing elements elem ....

scm_list_n takes a variable number of arguments, terminated by the special SCM_UNDEFINED. That final SCM_UNDEFINED is not included in the list. None of elem … can themselves be SCM_UNDEFINED, or scm_list_n will terminate at that point.

Scheme Procedure: cons* arg1 arg2 …

Like list, but the last arg provides the tail of the constructed list, returning (cons arg1 (cons arg2 (cons … argn))). Requires at least one argument. If given one argument, that argument is returned as result. This function is called list* in some other Schemes and in Common LISP.

Scheme Procedure: list-copy lst

C Function: scm_list_copy (lst)

Return a (newly-created) copy of lst.

Scheme Procedure: make-list n [init]

Create a list containing of n elements, where each element is initialized to init. init defaults to the empty list () if not given.

Note that list-copy only makes a copy of the pairs which make up the spine of the lists. The list elements are not copied, which means that modifying the elements of the new list also modifies the elements of the old list. On the other hand, applying procedures like set-cdr! or delv! to the new list will not alter the old list. If you also need to copy the list elements (making a deep copy), use the procedure copy-tree from (ice-9 copy-tree) (see Copying).