Re: Best way to check for an element in an array?
Hi,everyone,
This code must add the 'break',
import std.stdio;
int x=0;
template isin(T){
bool isin(T[] Array,T Element){
bool rtn=false;
foreach(T ArrayElement; Array){
if(Element==ArrayElement){
rtn=true; break; ← //here add break
}
x++;
}
return rtn;
}
}
void main(string[] args)
{
int[] stuff=[0,1,2,3,4,5,6,7,8,9,10]; ← //here declare int[]
if (stuff.isin(2)) // Much clean!
{
writeln(x);
writeln(Hello World!);
}
}
end---
Frank
Re: Best way to check for an element in an array?
Hi,everyone,
It works maybe the best:
import std.stdio;
template isin(T){
bool isin(T[] Array,T Element){
foreach(T ArrayElement; Array){
if(Element==ArrayElement){ return true;}
}
return false;
}
}
void main(string[] args)
{
int[] stuff=[0,1,2,3,4,5,6,7,8,9,10];
if (stuff.isin(2))
{
writeln(Hello World!);
}
string[] strs =[Hello,world,hi,Everyone];
if(strs.isin(Hi))
{
writeln(find Hi);
}
else
{
writeln(not find Hi from: ~strs);
}
}
end---
Frank
Re: Best way to check for an element in an array?
On Mon, 21 Apr 2014 23:25:39 -0400, Taylor Hillegeist
taylorh...@gmail.com wrote:
So I find myself Doing this kind of thing very frequently. I have a
Array of Somethings and i want to see if something specific is inside
the array. I wrote a template for it. but is this the best way to do
this kind of thing. I feel like it doesn't help with readability. Is
there a better way? Maybe i missed something in the std library.
import std.stdio;
Change this:
template FNDR(T){
To this:
template isIn(T) {
bool isIn(T Element, T[] Array){
bool rtn=false;
foreach(T ArrayElement; Array){
if(Element==ArrayElement){
rtn=true;
}
}
return rtn;
}
}
void main(string[] args)
{
int[3] stuff=[0,1,2];
if (FNDR!int.isIn(2,stuff))
now: if(isIn(2, stuff))
see implicit function template instantiation (IFTI) in docs.
Also, using UFCS (Unified Function Call Syntax (I think)), we can do:
if(2.isIn(stuff))
Or if you swap the parameters, and perhaps rename your template/function:
if(stuff.contains(2))
{
writeln(Hello World!);
}
}
-Steve
Best way to check for an element in an array?
So I find myself Doing this kind of thing very frequently. I have
a Array of Somethings and i want to see if something specific
is inside the array. I wrote a template for it. but is this the
best way to do this kind of thing. I feel like it doesn't help
with readability. Is there a better way? Maybe i missed something
in the std library.
import std.stdio;
template FNDR(T){
bool isIn(T Element, T[] Array){
bool rtn=false;
foreach(T ArrayElement; Array){
if(Element==ArrayElement){
rtn=true;
}
}
return rtn;
}
}
void main(string[] args)
{
int[3] stuff=[0,1,2];
if (FNDR!int.isIn(2,stuff))
{
writeln(Hello World!);
}
}
Is there a way maybe to make it look like this?
import std.stdio;
template FNDR(T){
bool contains(T[] Array,T Element){
bool rtn=false;
foreach(T ArrayElement; Array){
if(Element==ArrayElement){
rtn=true;
}
}
return rtn;
}
}
void main(string[] args)
{
int[3] stuff=[0,1,2];
if (stuff.contains(2)) // Much clean!
stuff.FNDR!int.contains(2) doesn't work
{
writeln(Hello World!);
}
}
I'm interested in what you guys think? what is the cleanest way
to do this?
Re: Best way to check for an element in an array?
you can use stuff.canFind(2)
but sometimes it'd be more convenient to have the other way around (UFCS
chains etc);
how about:
bool isIn(T,T2...)(T needle, T2 haystack)
if(__traits(compiles,T.init==T2[0].init)){
foreach(e;haystack){
if(needle==e) return true;
}
return false;
}
unittest{
assert(1.isIn(3,1,2) !4.isIn(3,1,2));
}
On Mon, Apr 21, 2014 at 8:25 PM, Taylor Hillegeist via Digitalmars-d-learn
digitalmars-d-learn@puremagic.com wrote:
So I find myself Doing this kind of thing very frequently. I have a Array
of Somethings and i want to see if something specific is inside the
array. I wrote a template for it. but is this the best way to do this kind
of thing. I feel like it doesn't help with readability. Is there a better
way? Maybe i missed something in the std library.
import std.stdio;
template FNDR(T){
bool isIn(T Element, T[] Array){
bool rtn=false;
foreach(T ArrayElement; Array){
if(Element==ArrayElement){
rtn=true;
}
}
return rtn;
}
}
void main(string[] args)
{
int[3] stuff=[0,1,2];
if (FNDR!int.isIn(2,stuff))
{
writeln(Hello World!);
}
}
Is there a way maybe to make it look like this?
import std.stdio;
template FNDR(T){
bool contains(T[] Array,T Element){
bool rtn=false;
foreach(T ArrayElement; Array){
if(Element==ArrayElement){
rtn=true;
}
}
return rtn;
}
}
void main(string[] args)
{
int[3] stuff=[0,1,2];
if (stuff.contains(2)) // Much clean! stuff.FNDR!int.contains(2)
doesn't work
{
writeln(Hello World!);
}
}
I'm interested in what you guys think? what is the cleanest way to do this?
Re: Best way to check for an element in an array?
On Tuesday, 22 April 2014 at 03:57:33 UTC, Timothee Cour via
Digitalmars-d-learn wrote:
you can use stuff.canFind(2)
but sometimes it'd be more convenient to have the other way
around (UFCS
chains etc);
how about:
bool isIn(T,T2...)(T needle, T2 haystack)
if(__traits(compiles,T.init==T2[0].init)){
foreach(e;haystack){
if(needle==e) return true;
}
return false;
}
unittest{
assert(1.isIn(3,1,2) !4.isIn(3,1,2));
}
I like it! I didn't know you could use templates like that!
Question though? why doesn't canFind() work on statically
allocated arrays?
import std.stdio;
import std.algorithm;
bool contains(T)( T[] haystack,T needle){
foreach(T e;haystack){
if(needle==e) return true;
}
return false;
}
unittest{
assert([3,1,2].contains(1) ![3,1,2].contains(4));
}
void main(string[] args)
{
int[3] stuff=[0,1,2];
if (stuff.contains(2))
{
writeln(Hello World!);
}
if (stuff.canFind(2)){ // No compile with stuff - static
writeln(This Also WOrks);
}
}
On Mon, Apr 21, 2014 at 8:25 PM, Taylor Hillegeist via
Digitalmars-d-learn
digitalmars-d-learn@puremagic.com wrote:
So I find myself Doing this kind of thing very frequently. I
have a Array
of Somethings and i want to see if something specific is
inside the
array. I wrote a template for it. but is this the best way to
do this kind
of thing. I feel like it doesn't help with readability. Is
there a better
way? Maybe i missed something in the std library.
import std.stdio;
template FNDR(T){
bool isIn(T Element, T[] Array){
bool rtn=false;
foreach(T ArrayElement; Array){
if(Element==ArrayElement){
rtn=true;
}
}
return rtn;
}
}
void main(string[] args)
{
int[3] stuff=[0,1,2];
if (FNDR!int.isIn(2,stuff))
{
writeln(Hello World!);
}
}
Is there a way maybe to make it look like this?
import std.stdio;
template FNDR(T){
bool contains(T[] Array,T Element){
bool rtn=false;
foreach(T ArrayElement; Array){
if(Element==ArrayElement){
rtn=true;
}
}
return rtn;
}
}
void main(string[] args)
{
int[3] stuff=[0,1,2];
if (stuff.contains(2)) // Much clean!
stuff.FNDR!int.contains(2)
doesn't work
{
writeln(Hello World!);
}
}
I'm interested in what you guys think? what is the cleanest
way to do this?
Re: Best way to check for an element in an array?
On 04/21/2014 09:22 PM, Taylor Hillegeist wrote:
Question though? why doesn't canFind() work on statically
allocated arrays?
That's an issue all of face from time to time. (Happened to me again
last week. :) )
The reason is, algorithms like canFind work with input ranges and
fixed-length arrays are not input ranges because they cannot support
popFront(), which would reduce their length.
The solution is to use a full slice of the array by appending [] to it:
if (stuff[].canFind(2)) {// -- note []
It works because now canFind() operates on a temporary slice (aka
dynamic array).
Getting back to your original question, std.algorithm.find and canFind()
are O(N) algorithms, which is too slow if you already have a sorted range.
When you indeed have a sorted range, you can pass it through
assumeSorted() to create a SortedRange object so that you can take
advantage of O(log N) algorithms like trisect() and friends (one of
those friends is contains()):
import std.range;
void main()
{
auto arr = [ 1, 2, 3, 3, 4, 5 ];
auto result = arr.assumeSorted.trisect(3);
assert(result[0].equal([ 1, 2 ]));
assert(result[1].equal([ 3, 3 ]));
assert(result[2].equal([ 4, 5 ]));
}
The search in that program is O(log N).
Ali
