Trying to invert a map and the following approach works fine:
var x = { 'dart' : 'fun', 'dentist' : 'painful', };
var xInv = x.keys.fold({}, (prev, elm) { prev[x[elm]] = elm; return prev; });
Is there a syntax to call 'operator[]=( , )' directly so you could also use cascades? Something like these which do not work:
var xInv = x.keys.fold({}, (prev, elm) => prev..'operator[]='(x[k], k));
var xInv = x.keys.fold({}, (prev, elm) => prev..operator[]=(x[k], k));
This is not what you want?
Map<String,String> xInv2 = x.keys.fold({},
(Map<String,String> prev, String elm) => prev..[x[elm]] = elm);
Creates the same result as your first example with the return statement.
(You don't have to add to add the type annotations though. It's just easier for me to grasp the intention of the code)
Related
I am looking for an alternative for this:
(?<=\.\d\d)\d
(Match third digit after a period.)
I'm aware I can solve it by using other methods, but I have to use a regular expression and more importantly I have to use replace on the string, without adding a callback.
Turn the lookbehind in a consuming pattern and use a capturing group:
And use it as shown below:
var s = "some string.005";
var rx = /\.\d\d(\d)/;
var m = s.match(/\.\d\d(\d)/);
if (m) {
console.log(m[1]);
}
Or, to get all matches:
const s = "some string.005 some string.006";
const rx = /\.\d\d(\d)/g;
let result = [], m;
while (m = rx.exec(s)) {
result.push(m[1]);
}
console.log( result );
An example with matchAll:
const result = Array.from(s.matchAll(rx), x=>x[1]);
EDIT:
To remove the 3 from the str.123 using your current specifications, use the same capturing approach: capture what you need and restore the captured text in the result using the $n backreference(s) in the replacement pattern, and just match what you need to remove.
var s = "str.123";
var rx = /(\.\d\d)\d/;
var res = s.replace(rx, "$1");
console.log(res);
How can I create multiple objects in 1 Step in Dart? Something like:
Class Player{
var Health;
var Level; .... }
Somewhere else:
Player[] player = new Player[20];
How can I do that in Dart?
If you wanna create a lot "Players"... Try this:
var players = List.generate(20, (i) => Player(/* properties */));
Filling in from any source, you can use the "i" as the index.
var players = List.generate(20, (i) {
var sourceRef = source[i];
return Player(
health: sourceRef["health"]
);
});
You can create a list of Player using the following line:
List<Player> player = new List(20);
And then initialize each object of your player list :
for (var i in jsonResponse['participants']) {
player[x] = new Player() ; // add this to your code
var fill = player[x];
fill.health = i['health'];
x++;
}
You can find more information about the proper way of building and initializing list in the official Dart Documentation.
I read the documentation (https://api.dartlang.org/stable/1.21.1/dart-core/RegExp-class.html) but could not find I was looking for. Either I didnt understand it or I overlooked something.
I am trying to replicate the following in google dart:
var regex = /foo_(\d+)/g,
str = "text foo_123 more text foo_456 foo_789 end text",
match = null;
while (match = regex.exec(str)) {
console.log(match); // matched capture groups
console.log(match.index); // index of where match starts in string
console.log(regex.lastIndex); // index of where match ends in string
}
I also created a jsfiddle: https://jsfiddle.net/h3z88udz/
Does dart have something like regex exec()?
RegExp.allMatches looks like it does what you want.
var regex = new RegExp(r"foo_(\d+)");
var str = "text foo_123 more text foo_456 foo_789 end text";
void main() {
for (var match in regex.allMatches(str)) {
print(match);
print(match.start);
print(match.end);
}
}
https://dartpad.dartlang.org/dd1c136fa49ada4f2ad4ffc0659aab51
Is it possible to filter numbers from the variable.
I can show you one example here from the link http://jsfiddle.net/sweetmaanu/82r5v/6/
I need to get only numbers from the alert message
Simply replace the box string out of it.
DEMO
for (var i = 0; i < order.length; i++) {
order[i] = order[i].replace('box', '');
}
So instead of box1, box2, box3, box4 you want to see 1,2,3,4
You can use a regular expression like this:
var order = $("#boxes").sortable("toArray") + "";
alert(order.replace(/[^0-9,]/g, ''));
I also had to append an empty string to order because it wasn't being recognized as a string object even though the jQuery documentation says it should be when you call sortable("toArray").
change var order = $("#boxes").sortable("toArray");
to var order = $("#boxes").sortable("toArray").join(',').replace(/[a-zA-Z]/gi, "");
Demo: http://jsfiddle.net/82r5v/13/
// Remove all non-digits from the string
'box1'.replace(/\D/g, ''); // => '1'
// Same, but try to make the string a number
Number('box1'.replace(/\D/g, '')); // => 1
// Shorthand for making an object a number (+o is the same as Number(o))
+'box1'.replace(/\D/g, ''); // => 1
// parseInt(s) works if the number is at the beginning
parseInt('1box'); // => 1
// but not if it occurs later
parseInt('box1'); // => NaN
Maybe using regular expressions something like this:
`alert(order.join(',').match(/\d/g));`
To return the array as numbers.
(\d matches all digits, g signifies a global match wildcard)
One way to do it by using regular expressions - http://jsfiddle.net/holodoc/82r5v/14/
$(document).ready(function() {
var arrValuesForOrder = ["2", "1", "3", "4"];
var ul = $("#boxes"),
items = $("#boxes li.con");
for (var i = arrValuesForOrder[arrValuesForOrder.length - 1]; i >= 0; i--) {
// arrValuesForOrder[i] element to move
// i = index to move element at
ul.prepend(items.get(arrValuesForOrder[i] - 1));
}
$("#boxes").sortable({
handle : '.drag',
update: function() {
var order = $("#boxes").sortable("toArray");
var sorted = [];
$.each(order, function(index, value){
sorted.push(value.match(/box(\d+)/)[1]);
})
alert(sorted);
}
});
});
I have to parse a document containing groups of variable-value-pairs which is serialized to a string e.g. like this:
4^26^VAR1^6^VALUE1^VAR2^4^VAL2^^1^14^VAR1^6^VALUE1^^
Here are the different elements:
Group IDs:
4^26^VAR1^6^VALUE1^VAR2^4^VAL2^^1^14^VAR1^6^VALUE1^^
Length of string representation of each group:
4^26^VAR1^6^VALUE1^VAR2^4^VAL2^^1^14^VAR1^6^VALUE1^^
One of the groups:
4^26^VAR1^6^VALUE1^VAR2^4^VAL2^^1^14 ^VAR1^6^VALUE1^^
Variables:
4^26^VAR1^6^VALUE1^VAR2^4^VAL2^^1^14^VAR1^6^VALUE1^^
Length of string representation of the values:
4^26^VAR1^6^VALUE1^VAR2^4^VAL2^^1^14^VAR1^6^VALUE1^^
The values themselves:
4^26^VAR1^6^VALUE1^VAR2^4^VAL2^^1^14^VAR1^6^VALUE1^^
Variables consist only of alphanumeric characters.
No assumption is made about the values, i.e. they may contain any character, including ^.
Is there a name for this kind of grammar? Is there a parsing library that can handle this mess?
So far I am using my own parser, but due to the fact that I need to detect and handle corrupt serializations the code looks rather messy, thus my question for a parser library that could lift the burden.
The simplest way to approach it is to note that there are two nested levels that work the same way. The pattern is extremely simple:
id^length^content^
At the outer level, this produces a set of groups. Within each group, the content follows exactly the same pattern, only here the id is the variable name, and the content is the variable value.
So you only need to write that logic once and you can use it to parse both levels. Just write a function that breaks a string up into a list of id/content pairs. Call it once to get the groups, and then loop through them calling it again for each content to get the variables in that group.
Breaking it down into these steps, first we need a way to get "tokens" from the string. This function returns an object with three methods, to find out if we're at "end of file", and to grab the next delimited or counted substring:
var tokens = function(str) {
var pos = 0;
return {
eof: function() {
return pos == str.length;
},
delimited: function(d) {
var end = str.indexOf(d, pos);
if (end == -1) {
throw new Error('Expected delimiter');
}
var result = str.substr(pos, end - pos);
pos = end + d.length;
return result;
},
counted: function(c) {
var result = str.substr(pos, c);
pos += c;
return result;
}
};
};
Now we can conveniently write the reusable parse function:
var parse = function(str) {
var parts = {};
var t = tokens(str);
while (!t.eof()) {
var id = t.delimited('^');
var len = t.delimited('^');
var content = t.counted(parseInt(len, 10));
var end = t.counted(1);
if (end !== '^') {
throw new Error('Expected ^ after counted string, instead found: ' + end);
}
parts[id] = content;
}
return parts;
};
It builds an object where the keys are the IDs (or variable names). I'm asuming as they have names that the order isn't significant.
Then we can use that at both levels to create the function to do the whole job:
var parseGroups = function(str) {
var groups = parse(str);
Object.keys(groups).forEach(function(id) {
groups[id] = parse(groups[id]);
});
return groups;
}
For your example, it produces this object:
{
'1': {
VAR1: 'VALUE1'
},
'4': {
VAR1: 'VALUE1',
VAR2: 'VAL2'
}
}
I don't think it's a trivial task to create a grammar for this. But on the other hand, a simple straight forward approach is not that hard. You know the corresponding string length for every critical string. So you just chop your string according to those lengths apart..
where do you see problems?