What is the best way to define and initialize a Table? - stanza

Question

In Python, we can do this.
board = {'us': {'name': 'USA', 'govern': 'good'},
'canada': {'name': 'Canada', 'govern': 'good'},
'uk': {'name': 'UK', 'govern': 'good', 'recruit': 3},
'spain': {'name': 'Spain', 'govern': 'good', 'schengen': True, 'recruit': 2},
'france': {'name': 'France', 'govern': 'good', 'schengen': True, 'recruit': 2},
'italy': {'name': 'italy', 'govern': 'good', 'schengen': True} }
to create a dictionary of name value pairs for easy lookup.
Can I the the same in Stanza language, like:
deftype Countries <: Table<String,Table<String,?>>
; value could be anything. we see Int|String|True|False here
val board : Countries = to-table( "us" => ( "name" => "USA", "govern" => "good" ), ....)
?

Answer 1

The closest data structure to a python dictionary in stanza is Hashtable, from collections. You can do something like :
; to-hashtable<K,V> can be found in collections, too!
val board = to-hashtable<String, HashTable<String, ?>> $ [
"us" => to-hashtable<String, ?> $ [
"name" => "USA"
],
"fr" => to-hashtable<String, ?> $ [
"name" => "France"
]
; .. etc ...
]
println(board["us"])
This will output :
HashTable(
"name" => "USA")
deftype Countries <: Table<...> doesn't create an alias for Table, it declares a new type. In order to use it like a table, you would need to implement the required methods for Table.
But normally we like to add more type information, not less!
defenum Government :
Democracy
Republic
Monarchy
defstruct Country :
name:String,
gov:Government
; ... etc ...
val board = to-hashtable<String,Country> $ [
"us" => Country(name, gov) where :
val name = "USA"
val gov = Republic
"fr" => Country(name, gov) where :
val name = "France"
val gov = Republic
]

Answer 2

I kind of come up with a solution:
defpackage labyrinth :
import core
import collections
deftype Countries <: HashTable<String,?>
defn print-deep ( xs : HashTable<String,?> ) :
for x in xs do :
val k = key(x)
val v = value(x)
print("%_ => " % [k])
match(v):
(v: HashTable<String,?>) : (print("[ "), print-deep(v), println("]"))
(v) : ( print(v), print(", ") )
defn to-hashtable ( t : HashTable<String,?>, kvs : Tuple<KeyValue<?,?>> ) -> False :
for kv in kvs do :
val k = key(kv)
val v = value(kv)
match(k) :
(k : String) :
if v is Tuple<?> :
var d : HashTable<String,?> = HashTable<String,?>()
to-hashtable(d, v)
set(t, k, d)
else :
t[k] = v
defn to-countries ( kvs : Tuple<KeyValue<String,?>> ) -> HashTable<String,?> :
val t : HashTable<String,?> = HashTable<String,?>()
to-hashtable(t, kvs)
t
defn test () -> HashTable<String,?> :
val c : Tuple<KeyValue<String,?>> =
[ "us" => ["name" => "us", "govern" => "good"]
"canada" => [ "name" => "Canada" "govern" => "good" ]
"uk" => [ "name" => "UK" "govern" => "good" "recruit" => 3 ]
"spain" => [ "name" => "Spain" "govern" => "good" "schengen" => true "recruit" => 2 ]
"france" => [ "name" => "France" "govern" => "good" "schengen" => true "recruit" => 2 ]
"italy" => [ "name" => "italy" "govern" => "good" "schengen" => true ]
]
val countries = to-countries(c)
countries
val board = test()
print-deep(board)