Examples of Setf Expansions

Examples of the contents of the constituents of setf expansions follow.

For a variable x:

() ;list of temporary variables () ;list of value forms (g0001) ;list of store variables (setq x g0001) ;storing form x ;accessing form

Figure 5--3: Sample Setf Expansion of a Variable

For (car exp):

(g0002) ;list of temporary variables (exp) ;list of value forms (g0003) ;list of store variables (progn (rplaca g0002 g0003) g0003) ;storing form (car g0002) ;accessing form

Figure 5--4: Sample Setf Expansion of a CAR Form

For (subseq seq s e):

(g0004 g0005 g0006) ;list of temporary variables (seq s e) ;list of value forms (g0007) ;list of store variables (progn (replace g0004 g0007 :start1 g0005 :end1 g0006) g0007) ;storing form (subseq g0004 g0005 g0006) ; accessing form

Figure 5--5: Sample Setf Expansion of a SUBSEQ Form

In some cases, if a subform of a place is itself a place, it is necessary to expand the subform in order to compute some of the values in the expansion of the outer place. For (ldb bs (car exp)):

(g0001 g0002) ;list of temporary variables (bs exp) ;list of value forms (g0003) ;list of store variables (progn (rplaca g0002 (dpb g0003 g0001 (car g0002))) g0003) ;storing form (ldb g0001 (car g0002)) ; accessing form

Figure 5--6: Sample Setf Expansion of a LDB Form

Go to the first, previous, next, last section, table of contents.