I am trying to create an empty map, that will be then populated within a for loop. Not sure how to proceed in Rascal. For testing purpose, I tried:
rascal>map[int, list[int]] x;
ok
Though, when I try to populate "x" using:
rascal>x += (1, [1,2,3])
>>>>>>>;
>>>>>>>;
^ Parse error here
I got a parse error.
To start, it would be best to assign it an initial value. You don't have to do this at the console, but this is required if you declare the variable inside a script. Also, if you are going to use +=, it has to already have an assigned value.
rascal>map[int,list[int]] x = ( );
map[int, list[int]]: ()
Then, when you are adding items into the map, the key and the value are separated by a :, not by a ,, so you want something like this instead:
rascal>x += ( 1 : [1,2,3]);
map[int, list[int]]: (1:[1,2,3])
rascal>x[1];
list[int]: [1,2,3]
An easier way to do this is to use similar notation to the lookup shown just above:
rascal>x[1] = [1,2,3];
map[int, list[int]]: (1:[1,2,3])
Generally, if you are just setting the value for one key, or are assigning keys inside a loop, x[key] = value is better, += is better if you are adding two existing maps together and saving the result into one of them.
I also like this solution sometimes, where you instead of joining maps just update the value of a certain key:
m = ();
for (...whatever...) {
m[key]?[] += [1,2,3];
}
In this code, when the key is not yet present in the map, then it starts with the [] empty list and then concatenates [1,2,3] to it, or if the key is present already, let's say it's already at [1,2,3], then this will create [1,2,3,1,2,3] at the specific key in the map.
Related
In GeoDMS, a geographic coding language by Object Vision, I cannot run code in GeoDmsRun.exe, which I could run without problems in GeoDmsGui.exe. The problem is that it cannot find the parameter 'Values' which is indeed not defined, but apparently implicit somewhere in GeoDMS. The GUI could find this parameter.
I tried defining the Values that lookup is looking for explicitly using
attribute<uint32>values1:=values;
But that didn't work. It would be best to get this lookup functionality without having to use any implicit variables, but how to do that?
Code:
unit<uint32> heatNet2 := unique(buildingWithHeatDemand/roadID)
, dialogType = 'map'
, dialogData = 'geometry'
{
attribute<rdc> geometry(arc) := lookup(values,input/geographic/roads/geometry);
}
Version: 7177
Thanks for helping!
The unique(D->V) operator indeed defines an attribute E->V with the name values of the resulting unit E that maps that resulting unit E to the found values of V. GeoDmsRun.exe should process scripts the same way as GeoDmsGui.exe does, so it is a good idea to report this as issue at http://www.mantis.objectvision.nl.
Meanwhile you can try to define the values attribute explicitly:
unit<uint32> heatNet2 := unique(buildingWithHeatDemand/roadID)
, dialogType = 'map'
, dialogData = 'geometry'
{
attribute<input/geographic/roads> values(heatNet2);
attribute<rdc> geometry(arc) := lookup(values,input/geographic/roads/geometry);
}
The now explicitly defined values will refer to the attribute of the result of the unique operator.
I'm trying to replace some characters in a String From a map
Case 1
map= ['O':'0', 'L':'1', 'Z':'2', 'E':'3']
"Hey".toUpperCase().toCharArray().each{
print map.get(it,it)
}
The result is
HEY
Case 2 : I dont use toCharArray()
"Hey".toUpperCase().each{
print map.get(it,it)
}
The result is like expected
H3Y
So I tried several alternatives when using toCharArray(), and the only way to access the value is to use map."$it"
Why i can only use map."$it" to access my map when using toCharArray() ?
Because you are trying to get a value from a map using a char whilst every key there are String, and they are not equals:
assert !'E'.equals('E' as char)
$it works because it is converted to String:
e = 'E' as char
assert "$e".toString().equals('E')
(Note the toString() is needed, otherwise the comparison will happen between String and GStringImpl which are not equals)
I'm trying to get the number of records with QML LocalStorage, which uses sqlite. Let's take this snippet in account:
function f() {
var db = LocalStorage.openDatabaseSync(...)
db.transaction (
function(tx) {
var b = tx.executeSql("SELECT * FROM t")
console.log(b.rows.length)
var c = tx.executeSql("SELECT COUNT(*) FROM t")
console.log(JSON.stringify(c))
}
)
}
The output is:
qml: 3
qml: {"rowsAffected":0,"insertId":"","rows":{}}
What am I doing wrong that the SELECT COUNT(*) doesn't output anything?
EDIT: rows only seems empty in the second command. Calling
console.log(JSON.stringify(c.rows.item(0)))
gives
qml: {"COUNT(*)":3}
Two questions now:
Why is rows shown as empty
How can I access the property inside c.rows.item(0)
In order to visit the items, you have to use:
b.rows.item(i)
Where i is the index of the item you want to get (in your first example, i belongs to [0, 1, 2] for you have 3 items, in the second one it is 0 and you can query it as c.rows.item(0)).
The rows field appears empty and it is a valid result, for the items are not part of the rows field itself (indeed you have to use a method to get them, as far as I know that method could also be a memento that completely enclose the response data) and the item method is probably defined as not enumerable (I cannot verify it, I'm on the beach and it's quite difficult to explore the Qt code now :-)). You can safely rely on the length parameter to know if there are returned values, thus you can iterate over them to print them out. I did something like that in a project of mine and it works fine.
The properties inside item(0) have the same names given for the query. I suggest to rewrite that query as:
select count(*) as cnt from t
Then, you can get the count as:
c.rows.item(0).cnt
can anyone explain why line 1 works to create an empty swift dictionary but line 2 doesn't when i try to create a swift dictionary with int key and tuple of double values .... how should it be done?
var testDic2 = [Int:Double]()
var testDic3 = [Int:(Double,Double)]()
I've tried various combinations in playgrounds and the only version where it doesnt give me a compiler error is as follows
var possibleTips = [Int(): (tipAmt:Double(), total:Double())]
but im not sure this last form is declaring the dictionary as i intend it (ie as per testDict3 above)
The compiler isn't sure how to instantiate the type in your second and third example. Instead, you can declare the type and use an empty dictionary initializer:
var testDic:[Int:(Double,Double)] = [:]
I'm messing around a bit with F# and I'm not quite sure if I'm doing this correctly. In C# this could be done with an IDictionary or something similar.
type School() =
member val Roster = Map.empty with get, set
member this.add(grade: int, studentName: string) =
match this.Roster.ContainsKey(grade) with
| true -> // Can I do something like this.Roster.[grade].Insert([studentName])?
| false -> this.Roster <- this.Roster.Add(grade, [studentName])
Is there a way to insert into the map if it contains a specified key or am I just using the wrong collection in this case?
The F# Map type is a mapping from keys to values just like ordinary .NET Dictionary, except that it is immutable.
If I understand your aim correctly, you're trying to keep a list of students for each grade. The type in that case is a map from integers to lists of names, i.e. Map<int, string list>.
The Add operation on the map actually either adds or replaces an element, so I think that's the operation you want in the false case. In the true case, you need to get the current list, append the new student and then replace the existing record. One way to do this is to write something like:
type School() =
member val Roster = Map.empty with get, set
member this.Add(grade: int, studentName: string) =
// Try to get the current list of students for a given 'grade'
let studentsOpt = this.Roster.TryFind(grade)
// If the result was 'None', then use empty list as the default
let students = defaultArg studentsOpt []
// Create a new list with the new student at the front
let newStudents = studentName::students
// Create & save map with new/replaced mapping for 'grade'
this.Roster <- this.Roster.Add(grade, newStudents)
This is not thread-safe (because calling Add concurrently might not update the map properly). However, you can access school.Roster at any time, iterate over it (or share references to it) safely, because it is an immutable structure. However, if you do not care about that, then using standard Dictionary would be perfectly fine too - depends on your actual use case.