I want To build a Program in which i want Multiple inputs in integers and Reverse it .. how Can I Do that in Dart?
I tried of strings But Don't Know About Integers
You can do something like this:
import 'dart:io';
void main() {
print('Input integers (q to stop):');
final integers = <int>[];
while (true) {
// Reads input from the user.
final input = stdin.readLineSync()!;
// Check to see if the user is done inputting numbers.
if (input == 'q') {
break;
}
// Try to convert the String to an int. If input isn't a
// valid integer, int.tryParse(input) == null.
final integer = int.tryParse(input);
if (integer != null) {
integers.add(integer);
}
}
print('Original order: $integers');
// Reversing a List in Dart is simple: just call integers.reverse
// to get an Iterable with the elements of integers in reversed order.
// Calling integers.reverse.toList() will convert the Iterable to a List
// so it's possible to print the entire list at once.
print('Reversed order: ${integers.reversed.toList()}');
}
Example:
Input integers (q to stop):
1
2
3
r
4
5
q
Original order: [1, 2, 3, 4, 5]
Reversed order: [5, 4, 3, 2, 1]
import 'dart:io';
void main() {
int? n = int.parse(stdin.readLineSync()!);
print("value of n: $n and run time type: ${n.runtimeType}");
List<int> list1 = [];
for (int i = 0; i < n; i++) {
list1.insert(i, int.parse(stdin.readLineSync()!));
}
print("List 1: $list1");
}
This is my code.
If I take in put like that:
5
1
2
3
4
5
it gives output:
value of n: 5 and run time type: int
List 1: [1, 2, 3, 4, 5]
I want to take input like:
5
1 2 3 4 5
and want the same output. But I do not find any resources for that. Please help me.
You can split the string by using space as delimiter and then use map to parse each string into an int.
This way don't need to know number of elements beforehand but if it's necessary to get exactly n number of elements in list then you can use Iterable.take() method.
List<int> list1 = stdin
.readLineSync()
?.split(RegExp(r'\s+'))
.map((e) => int.parse(e))
.take(n)
.toList() ??
List<int>.empty();
I have the following math operation:
var _baseFontSize = _userfontsize*8;
if (_baseFontSize > 14) { _baseFontSize = 14.0; }
Essentially whatever the _userfontsize is, my _baseFontSize should be 8x that number, but never exceeding 14.0.
Instead of doing this math operation in 2 lines as might be conventional, is there a way to set a max limit to this (or any given) math operation in dart?
You can import dart:math and do something like this with min:
var _baseFontSize = min(_userfontsize * 8, 14.0);
T min<T extends num>(T a, T b)
Returns the lesser of two numbers.
Let's say I want to process a variadic function which alternately gets passed start and end values of 1 or more intervals and it should return a range of random values in those intervals. You can imagine the input to be a flattened sequence of tuples, all tuple elements spread over one single range.
import std.meta; //variadic template predicates
import std.traits : isFloatingPoint;
import std.range;
auto randomIntervals(T = U[0], U...)(U intervals)
if (U.length/2 > 0 && isFloatingPoint!T && NoDuplicates!U.length == 1) {
import std.random : uniform01;
T[U.length/2] randomValues;
// split and iterate over subranges of size 2
foreach(i, T start, T end; intervals.chunks(2)) { //= intervals.slide(2,2)
randomValues[i] = uniform01 * (end - start) + start,
}
return randomValues.dup;
}
The example is not important, I only use it for explanation. The chunk size could be any finite positive size_t, not only 2 and changing the chunk size should only require changing the number of loop-variables in the foreach loop.
In this form above it will not compile since it would only expect one argument (a range) to the foreach loop. What I would like is something which rather automatically uses or infers a sliding-window as a tuple, derived from the number of given loop-variables, and fills the additional variables with next elements of the range/array + allows for an additional index, optionally. According to the documentation a range of tuples allows destructuring of the tuple elements in place into foreach-loop-variables so the first thing, I thought about, is turning a range into a sequence of tuples but didn't find a convenience function for this.
Is there a simple way to loop over destructured subranges (with such a simplicity as shown in my example code) together with the index? Or is there a (standard library) function which does this job of splitting a range into enumerated tuples of equal size? How to easily turn the range of subranges into a range of tuples?
Is it possible with std.algorithm.iteration.map in this case (EDIT: with a simple function argument to map and without accessing tuple elements)?
EDIT: I want to ignore the last chunk which doesn't fit into the entire tuple. It just is not iterated over.
EDIT: It's not, that I couldn't program this myself, I only hope for a simple notation because this use case of looping over multiple elements is quite useful. If there is something like a "spread" or "rest" operator in D like in JavaScript, please let me know!
Thank you.
(Added as a separate answer because it's significantly different from my previous answer, and wouldn't fit in a comment)
After reading your comments and the discussion on the answers thus far, it seems to me what you seek is something like the below staticChunks function:
unittest {
import std.range : enumerate;
size_t index = 0;
foreach (i, a, b, c; [1,2,3,1,2,3].staticChunks!3.enumerate) {
assert(a == 1);
assert(b == 2);
assert(c == 3);
assert(i == index);
++index;
}
}
import std.range : isInputRange;
auto staticChunks(size_t n, R)(R r) if (isInputRange!R) {
import std.range : chunks;
import std.algorithm : map, filter;
return r.chunks(n).filter!(a => a.length == n).map!(a => a.tuplify!n);
}
auto tuplify(size_t n, R)(R r) if (isInputRange!R) {
import std.meta : Repeat;
import std.range : ElementType;
import std.typecons : Tuple;
import std.array : front, popFront, empty;
Tuple!(Repeat!(n, ElementType!R)) result;
static foreach (i; 0..n) {
result[i] = r.front;
r.popFront();
}
assert(r.empty);
return result;
}
Note that this also deals with the last chunk being a different size, if only by silently throwing it away. If this behavior is undesirable, remove the filter, and deal with it inside tuplify (or don't, and watch the exceptions roll in).
chunks and slide return Ranges, not tuples. Their last element can contain less than the specified size, whereas tuples have a fixed compile time size.
If you need destructuring, you have to implement your own chunks/slide that return tuples. To explicitly add an index to the tuple, use enumerate. Here is an example:
import std.typecons, std.stdio, std.range;
Tuple!(int, int)[] pairs(){
return [
tuple(1, 3),
tuple(2, 4),
tuple(3, 5)
];
}
void main(){
foreach(size_t i, int start, int end; pairs.enumerate){
writeln(i, ' ', start, ' ', end);
}
}
Edit:
As BioTronic said using map is also possible:
foreach(i, start, end; intervals
.chunks(2)
.map!(a => tuple(a[0], a[1]))
.enumerate){
Your question has me a little confused, so I'm sorry if I've misunderstood. What you're basically asking is if foreach(a, b; [1,2,3,4].chunks(2)) could work, right?
The simple solution here is to, as you say, map from chunk to tuple:
import std.typecons : tuple;
import std.algorithm : map;
import std.range : chunks;
import std.stdio : writeln;
unittest {
pragma(msg, typeof([1,2].chunks(2).front));
foreach(a, b; [1,2,3,4].chunks(2).map!(a => tuple(a[0], a[1]))) {
writeln(a, ", ", b);
}
}
At the same time with BioTronic, I tried to code some own solution to this problem (tested on DMD). My solution works for slices (BUT NOT fixed-size arrays) and avoids a call to filter:
import std.range : chunks, isInputRange, enumerate;
import std.range : isRandomAccessRange; //changed from "hasSlicing" to "isRandomAccessRange" thanks to BioTronics
import std.traits : isIterable;
/** turns chunks into tuples */
template byTuples(size_t N, M)
if (isRandomAccessRange!M) { //EDITED
import std.meta : Repeat;
import std.typecons : Tuple;
import std.traits : ForeachType;
alias VariableGroup = Tuple!(Repeat!(N, ForeachType!M)); //Tuple of N repititions of M's Foreach-iterated Type
/** turns N consecutive array elements into a Variable Group */
auto toTuple (Chunk)(Chunk subArray) #nogc #safe pure nothrow
if (isInputRange!Chunk) { //Chunk must be indexable
VariableGroup nextLoopVariables; //fill the tuple with static foreach loop
static foreach(index; 0 .. N) {
static if ( isRandomAccessRange!Chunk ) { // add cases for other ranges here
nextLoopVariables[index] = subArray[index];
} else {
nextLoopVariables[index] = subArray.popFront();
}
}
return nextLoopVariables;
}
/** returns a range of VariableGroups */
auto byTuples(M array) #safe pure nothrow {
import std.algorithm.iteration : map;
static if(!isInputRange!M) {
static assert(0, "Cannot call map() on fixed-size array.");
// auto varGroups = array[].chunks(N); //fixed-size arrays aren't slices by default and cannot be treated like ranges
//WARNING! invoking "map" on a chunk range from fixed-size array will fail and access wrong memory with no warning or exception despite #safe!
} else {
auto varGroups = array.chunks(N);
}
//remove last group if incomplete
if (varGroups.back.length < N) varGroups.popBack();
//NOTE! I don't know why but `map!toTuple` DOES NOT COMPILE! And will cause a template compilation mess.
return varGroups.map!(chunk => toTuple(chunk)); //don't know if it uses GC
}
}
void main() {
testArrayToTuples([1, 3, 2, 4, 5, 7, 9]);
}
// Order of template parameters is relevant.
// You must define parameters implicitly at first to be associated with a template specialization
void testArrayToTuples(U : V[], V)(U arr) {
double[] randomNumbers = new double[arr.length / 2];
// generate random numbers
foreach(i, double x, double y; byTuples!2(arr).enumerate ) { //cannot use UFCS with "byTuples"
import std.random : uniform01;
randomNumbers[i] = (uniform01 * (y - x) + x);
}
foreach(n; randomNumbers) { //'n' apparently works despite shadowing a template parameter
import std.stdio : writeln;
writeln(n);
}
}
Using elementwise operations with the slice operator would not work here because uniform01 in uniform01 * (ends[] - starts[]) + starts[] would only be called once and not multiple times.
EDIT: I also tested some online compilers for D for this code and it's weird that they behave differently for the same code. For compilation of D I can recommend
https://run.dlang.io/ (I would be very surprised if this one wouldn't work)
https://www.mycompiler.io/new/d (but a bit slow)
https://ideone.com (it works but it makes your code public! Don't use with protected code.)
but those didn't work for me:
https://tio.run/#d2 (didn't finish compilation in one case, otherwise wrong results on execution even when using dynamic array for the test)
https://www.tutorialspoint.com/compile_d_online.php (doesn't compile the static foreach)
Maybe I'm missing a keyword in my searches for a solution, but I didn't find what I'm looking for.
In Google Sheets I want to take a set of numbers and reorder it randomly. For example, start with the set [1,2,3,4] and get back [4,2,1,3].
Any ideas which function or a combination of functions may achieve this goal?
The entire process that I want to achieve is something like this:
I have a set of 4 fields. Their sum is fixed. I want to assign them randomized values.
So, I was thinking to iterate through this process:
Create a random integer between 0 and the max possible value (in the first iteration it's the fixed sum)
The new max value is the last max value minus the new random number.
Check if the new max is zero.
If not:
Return to the 1st step and repeat - This goes on until there are four values
If needed the 4th value shall be increased so the total will match the fixed sum.
Else, continue.
Randomize the order of the 4 values.
Assign the values to the 4 fields.
try:
=INDEX(SORT({{1; 2; 3; 4}, RANDARRAY(4, 1)}, 2, ),, 1)
or:
=INDEX(SORT({ROW(1:4), RANDARRAY(4, 1)}, 2, ),, 1)
Here are a couple of app script examples as well
function DiceRolls(nNumRolls) {
var anRolls = [];
nNumRolls = DefaultTo(nNumRolls, 1000)
for (var i = 1;i <= nNumRolls; i++) {
anRolls.push(parseInt((Math.random() * 6))+1);
}
return anRolls;
}
function CoinFlips(nNumFlips) {
var anFlips = [];
nNumFlips = DefaultTo(nNumFlips, 1000)
for (var i = 1;i <= nNumFlips; i++) {
anFlips.push(getRndInteger(1,2));
}
return anFlips;
}
function getRndInteger(min, max) {
return Math.floor(Math.random() * (max - min + 1) ) + min;
}