11. References and Records

#-----------------------------
module "/pliant/lnaguage/unsafe.pli" # using pointers is unsafe
var Pointer:Int sref  # declaration of a reference to an Int
sref :> value         # reference assignment (sref "points" to value content)
#-----------------------------
var Link:Int sref2    # declaration of a link (concerns object, increments reference count)
sref2 :> new Int      # typical use of "new" to create a new object
#-----------------------------
console sref # prints the scalar value that the reference sref refers to
sref := 3    # assigns to sref's referent
#-----------------------------
var Pointer:(Array:Int) aref :> array
#-----------------------------
sref :> null map Int
sref := 4            # runtime error
#-----------------------------
var Link:(Array Int) aref :> new Array:Int    # new array
aref += 3; aref += 4; aref += 5
gvar Link:(Dictionary Str Str) href :> new (Dictionary Str Str) # new hash
implicit href
  insert "How" "Now"
  insert "Brown" "Cow"
#-----------------------------
aref :> null map Array:Int
aref :> new Array:Int
console (cast addressof:aref Int)
1076501816
#-----------------------------

#-----------------------------
aref :> array
anon_array :> new Array:Int; annon_array += 1; annon_array += 3;
annon_array += 5; annon_array += 7; annon_array += 9;
#-----------------------------
annon_array += 11
#-----------------------------
one := annon_array 0
#-----------------------------
num_items := aref size
#-----------------------------
# check whether an Arrow is the address of an array of Int
if entry_type:arrow <> Array:Int
  error error_id_unexpected "Expected an array reference, not "+entry_type:arrow:name
  return

array_ref += item # append new element to orig array
#-----------------------------
function array_ref -> ref
  arg Link:(Array:Int) ref
  gvar Array:Int array
  ref :> array

var Link:(Array:Int) aref1 :> array_ref
var Link:(Array:Int) aref2 :> array_ref
#-----------------------------
console array_ref:n            # access item in position n
#-----------------------------
each item array_ref
  # item has data

for (var Int idx) 0 array_ref:size-1
  # array_ref:idx has data
#-----------------------------

#-----------------------------
var Link:(Dictionary Str Str) href :> hash
var Link:(Dictionary Str Str) anon_hash
implicit anon_hash
  insert "key1" "value1"
  insert "key2" "value2"
#-----------------------------
value := href key
#-----------------------------
if entry_type:arrow <> (Dictionary Str Str)
  error error_id_unexpected "Expected a has reference, not "+entry_type:arrow:name
#-----------------------------
each item href
  console (href key item) " => " item eol
#-----------------------------

#-----------------------------
module "/pliant/language/compiler.pli" # access to Function type
function thefunc s -> i
  arg Str s; arg Int i
  #...
var Link:Function fun :> the_function thefunc Str -> Int

function wrapper s f -> i               # used to perform an indirect call
  arg Str s; arg Function f; arg Int i
  indirect

value := wrapper "hello" fun            # actually calls the_func 
#-----------------------------
var (Dictionary Str (Link Function)) commands   # Function may not be copied, use links.
var Link:Function fun
implicit commands
  fun :> thefunction joy -> Str; insert "happy" fun
  fun :> thefunction sullen -> Str; insert "sad" fun
  fun :> thefunction angry -> Str; insert "mad" fun

module "/pliant/language/ui/ansi_terminal.pli" # access to terminal functions
var Str string := keyboard_input "How are you? "

function wrapper2 fun -> s  # wrapper function for indirect call
  arg Function fun; arg Str s
  indirect
  
if (commands exists string)
  console (wrapper2 commands:string) eol
else
  console "No such command : " string eol
#-----------------------------
type Counter
  field Int start <- 0

function 'cast Int' c -> i   # counter is incremented when used as an Int
  arg Counter c; arg Int i
  implicit
  i := c start
  (addressof c:start) map Int += 1

function make_counter -> counter
  arg Link:Counter counter
  counter :> new Counter

var Link:Counter counter :> counter_maker
for (var Int i) 0 5
  var Int value := counter; console value eol
#-----------------------------
var Link:Counter counter1 :> counter_maker
var Link:Counter counter2 :> counter_maker

for (var Int i) 0 5
  var Int value := counter1; console value eol

console (cast counter1 Int) " " (cast counter2 Int) eol
0
1
2
3
4
5 0
#-----------------------------

#-----------------------------
scalar_ref :> scalar         # get reference to named scalar
#-----------------------------
console scalar_ref           # dereference it
scalar_ref := 23             # alter referent's value
#-----------------------------
function new_anon_scalar -> s
  arg Link:Int s
  s :> new Int
#-----------------------------
sref :> new_anon_scalar
sref := 3
console "Three = " sref eol
#-----------------------------------