hyung-hwan
46dd217591
various bug fixes in dealing with multiple instances - still more to fix more methods to dictionary access files to access cons cell to the core module
80 lines
2.5 KiB
Plaintext
80 lines
2.5 KiB
Plaintext
## core.car / core.cdr / core.cons
|
|
##
|
|
## A data list #(1 2 3) is a chain of Cons cells whose head and tail live in
|
|
## named instance variables, so basicAt and primAt cannot reach them. These
|
|
## three are what let the class library walk and build a list.
|
|
|
|
fun chk(ok msg) {
|
|
if ok { printf "OK: %s\n" msg } \
|
|
else { printf "ERROR: %s\n" msg }
|
|
}
|
|
|
|
l := #(1 2 3)
|
|
chk (eqv? (core.classOf l) Cons) "a data list is a chain of Cons cells"
|
|
chk (= (core.car l) 1) "car answers the head"
|
|
chk (eqv? (core.classOf (core.cdr l)) Cons) "cdr answers the tail"
|
|
chk (= (core.car (core.cdr l)) 2) "cadr reaches the second element"
|
|
chk (nil? (core.cdr (core.cdr (core.cdr l)))) "the tail of the last cell is nil"
|
|
|
|
## walking
|
|
n := 0
|
|
sum := 0
|
|
p := l
|
|
while (not (nil? p)) {
|
|
n := (+ n 1)
|
|
sum := (+ sum (core.car p))
|
|
p := (core.cdr p)
|
|
}
|
|
chk (= n 3) "a list can be walked to its end"
|
|
chk (= sum 6) "and every element visited"
|
|
|
|
## building
|
|
b := (core.cons 1 (core.cons 2 (core.cons 3 nil)))
|
|
chk (eqv? (core.classOf b) Cons) "cons builds a cell"
|
|
chk (= (core.car b) 1) "the built list starts where it should"
|
|
chk (= (core.car (core.cdr (core.cdr b))) 3) "and ends where it should"
|
|
chk (nil? (core.cdr (core.cdr (core.cdr b)))) "and is properly terminated"
|
|
|
|
## an improper list is allowed - the tail need not be a list
|
|
i := (core.cons 1 2)
|
|
chk (= (core.cdr i) 2) "cons accepts a non-list tail"
|
|
|
|
## select over a list, species preserved, built with cons alone
|
|
fun l-reverse(l) {
|
|
| p out |
|
|
out := nil
|
|
p := l
|
|
while (not (nil? p)) {
|
|
out := (core.cons (core.car p) out)
|
|
p := (core.cdr p)
|
|
}
|
|
return out
|
|
}
|
|
fun l-select(l blk) {
|
|
| p out x |
|
|
out := nil
|
|
p := l
|
|
while (not (nil? p)) {
|
|
x := (core.car p)
|
|
if (blk x) { out := (core.cons x out) }
|
|
p := (core.cdr p)
|
|
}
|
|
return (l-reverse out)
|
|
}
|
|
v := #(1 2 3 4 5 6)
|
|
r := (l-select v (fun(x) { return (= 0 (rem x 2)) }))
|
|
chk (eqv? (core.classOf r) Cons) "select over a list answers a list"
|
|
chk (= (core.car r) 2) "with the right first element"
|
|
chk (= (core.car (core.cdr r)) 4) "and the right second"
|
|
chk (= (core.car (core.cdr (core.cdr r))) 6) "and the right third"
|
|
chk (nil? (core.cdr (core.cdr (core.cdr r)))) "and nothing more"
|
|
chk (= (core.car v) 1) "the original list is untouched"
|
|
|
|
## the type gate
|
|
bad := 0
|
|
try { core.car nil } catch (e) { bad := (+ bad 1) }
|
|
try { core.cdr nil } catch (e) { bad := (+ bad 1) }
|
|
try { core.car #[1 2] } catch (e) { bad := (+ bad 1) }
|
|
try { core.cdr "s" } catch (e) { bad := (+ bad 1) }
|
|
chk (= bad 4) "car and cdr refuse anything that is not a cons"
|