# 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-ingredients result <- new {(list _elem): type} *result <- merge x, l ] def first in:&:list:_elem -> result:_elem [ local-scope load-ingredients result <- get *in, value:offset ] def rest in:&:list:_elem -> result:&:list:_elem/contained-in:in [ local-scope load-ingredients result <- get *in, next:offset ] scenario list-handling [ run [ local-scope x:&:list:num <- push 3, 0 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-ingredients 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-ingredients 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, 0 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, 0 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, 0 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-ingredients # if 'x' is null, return return-unless x next-node:&:list:_elem <- rest x # clear next pointer of 'x' *x <- put *x, next:offset, 0 # 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, 0 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, 0 # 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, 0 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, 0 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, 0 # 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, 0 run [ list <- remove list, list 1:num/raw <- copy 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-ingredients return-unless list, temp object:_elem <- first, list list <- rest list temp <- push object, temp result <- reverse list,