# A list links up multiple objects together to make them easier to manage.
#
# The objects must be of the same type. If you want to store multiple types in
# a single list, use an exclusive-container.
container list:_elem [
value:_elem
next:&:list:_elem
]
def push x:_elem, l:&:list:_elem -> result:&:list:_elem/contained-in:l [
local-scope
load-inputs
result <- new {(list _elem): type}
*result <- merge x, l
]
def first in:&:list:_elem -> result:_elem [
local-scope
load-inputs
result <- get *in, value:offset
]
def rest in:&:list:_elem -> result:&:list:_elem/contained-in:in [
local-scope
load-inputs
result <- get *in, next:offset
]
scenario list-handling [
run [
local-scope
x:&:list:num <- push 3, null
x <- push 4, x
x <- push 5, x
10:num/raw <- first x
x <- rest x
11:num/raw <- first x
x <- rest x
12:num/raw <- first x
20:&:list:num/raw <- rest x
]
memory-should-contain [
10 <- 5
11 <- 4
12 <- 3
20 <- 0 # nothing left
]
]
def length l:&:list:_elem -> result:num [
local-scope
load-inputs
result <- copy 0
{
break-unless l
result <- add result, 1
l <- rest l
loop
}
]
# insert 'x' after 'in'
def insert x:_elem, in:&:list:_elem -> in:&:list:_elem [
local-scope
load-inputs
new-node:&:list:_elem <- new {(list _elem): type}
*new-node <- put *new-node, value:offset, x
next-node:&:list:_elem <- get *in, next:offset
*in <- put *in, next:offset, new-node
*new-node <- put *new-node, next:offset, next-node
]
scenario inserting-into-list [
local-scope
list:&:list:num <- push 3, null
list <- push 4, list
list <- push 5, list
run [
list2:&:list:num <- rest list # inside list
list2 <- insert 6, list2
# check structure
list2 <- copy list
10:num/raw <- first list2
list2 <- rest list2
11:num/raw <- first list2
list2 <- rest list2
12:num/raw <- first list2
list2 <- rest list2
13:num/raw <- first list2
]
memory-should-contain [
10 <- 5 # scanning next
11 <- 4
12 <- 6 # inserted element
13 <- 3
]
]
scenario inserting-at-end-of-list [
local-scope
list:&:list:num <- push 3, null
list <- push 4, list
list <- push 5, list
run [
list2:&:list:num <- rest list # inside list
list2 <- rest list2 # now at end of list
list2 <- insert 6, list2
# check structure like before
list2 <- copy list
10:num/raw <- first list2
list2 <- rest list2
11:num/raw <- first list2
list2 <- rest list2
12:num/raw <- first list2
list2 <- rest list2
13:num/raw <- first list2
]
memory-should-contain [
10 <- 5 # scanning next
11 <- 4
12 <- 3
13 <- 6 # inserted element
]
]
scenario inserting-after-start-of-list [
local-scope
list:&:list:num <- push 3, null
list <- push 4, list
list <- push 5, list
run [
list <- insert 6, list
# check structure like before
list2:&:list:num <- copy list
10:num/raw <- first list2
list2 <- rest list2
11:num/raw <- first list2
list2 <- rest list2
12:num/raw <- first list2
list2 <- rest list2
13:num/raw <- first list2
]
memory-should-contain [
10 <- 5 # scanning next
11 <- 6 # inserted element
12 <- 4
13 <- 3
]
]
# remove 'x' from its surrounding list 'in'
#
# Returns null if and only if list is empty. Beware: in that case any other
# pointers to the head are now invalid.
def remove x:&:list:_elem/contained-in:in, in:&:list:_elem -> in:&:list:_elem [
local-scope
load-inputs
# if 'x' is null, return
return-unless x
next-node:&:list:_elem <- rest x
# clear next pointer of 'x'
*x <- put *x, next:offset, null
# if 'x' is at the head of 'in', return the new head
at-head?:bool <- equal x, in
return-if at-head?, next-node
# compute prev-node
prev-node:&:list:_elem <- copy in
curr:&:list:_elem <- rest prev-node
{
return-unless curr
found?:bool <- equal curr, x
break-if found?
prev-node <- copy curr
curr <- rest curr
}
# set its next pointer to skip 'x'
*prev-node <- put *prev-node, next:offset, next-node
]
scenario removing-from-list [
local-scope
list:&:list:num <- push 3, null
list <- push 4, list
list <- push 5, list
run [
list2:&:list:num <- rest list # second element
list <- remove list2, list
10:bool/raw <- equal list2, null
# check structure like before
list2 <- copy list
11:num/raw <- first list2
list2 <- rest list2
12:num/raw <- first list2
20:&:list:num/raw <- rest list2
]
memory-should-contain [
10 <- 0 # remove returned non-null
11 <- 5 # scanning next, skipping deleted element
12 <- 3
20 <- 0 # no more elements
]
]
scenario removing-from-start-of-list [
local-scope
list:&:list:num <- push 3, null
list <- push 4, list
list <- push 5, list
run [
list <- remove list, list
# check structure like before
list2:&:list:num <- copy list
10:num/raw <- first list2
list2 <- rest list2
11:num/raw <- first list2
20:&:list:num/raw <- rest list2
]
memory-should-contain [
10 <- 4 # scanning next, skipping deleted element
11 <- 3
20 <- 0 # no more elements
]
]
scenario removing-from-end-of-list [
local-scope
list:&:list:num <- push 3, null
list <- push 4, list
list <- push 5, list
run [
# delete last element
list2:&:list:num <- rest list
list2 <- rest list2
list <- remove list2, list
10:bool/raw <- equal list2, null
# check structure like before
list2 <- copy list
11:num/raw <- first list2
list2 <- rest list2
12:num/raw <- first list2
20:&:list:num/raw <- rest list2
]
memory-should-contain [
10 <- 0 # remove returned non-null
11 <- 5 # scanning next, skipping deleted element
12 <- 4
20 <- 0 # no more elements
]
]
scenario removing-from-singleton-list [
local-scope
list:&:list:num <- push 3, null
run [
list <- remove list, list
1:num/raw <- deaddress list
]
memory-should-contain [
1 <- 0 # back to an empty list
]
]
# reverse the elements of a list
# (contributed by Caleb Couch)
def reverse list:&:list:_elem temp:&:list:_elem/contained-in:result -> result:&:list:_elem [
local-scope
load-inputs
return-unless list, temp
object:_elem <- first, list
list <- rest list
temp <- push object, temp
result <- reverse list, temp
]
scenario reverse-list [
local-scope
list:&:list:num <- push 1, null
list <- push 2, list
list <- push 3, list
run [
stash [list:], list
list <- reverse list
stash [reversed:], list
]
trace-should-contain [
app: list: 3 -> 2 -> 1
app: reversed: 1 -> 2 -> 3
]
]
scenario stash-list [
local-scope
list:&:list:num <- push 1, null
list <- push 2, list
list <- push 3, list
run [
stash [list:], list
]
trace-should-contain [
app: list: 3 -> 2 -> 1
]
]
def to-text in:&:list:_elem -> result:text [
local-scope
load-inputs
buf:&:buffer:char <- new-buffer 80
buf <- to-buffer in, buf
result <- buffer-to-array buf
]
# variant of 'to-text' which stops printing after a few elements (and so is robust to cycles)
def to-text-line in:&:list:_elem -> result:text [
local-scope
load-inputs
buf:&:buffer:char <- new-buffer 80
buf <- to-buffer in, buf, 6 # max elements to display
result <- buffer-to-array buf
]
def to-buffer in:&:list:_elem, buf:&:buffer:char -> buf:&:buffer:char [
local-scope
load-inputs
{
break-if in
buf <- append buf, [[]]
return
}
# append in.value to buf
val:_elem <- get *in, value:offset
buf <- append buf, val
# now prepare next
next:&:list:_elem <- rest in
nextn:num <- deaddress next
return-unless next
buf <- append buf, [ -> ]
# and recurse
remaining:num, optional-input-found?:bool <- next-input
{
break-if optional-input-found?
# unlimited recursion
buf <- to-buffer next, buf
return
}
{
break-unless remaining
# limited recursion
remaining <- subtract remaining, 1
buf <- to-buffer next, buf, remaining
return
}
# past recursion depth; insert ellipses and stop
append buf, [...]
]
scenario stash-empty-list [
local-scope
x:&:list:num <- copy null
run [
stash x
]
trace-should-contain [
app: []
]
]