Programming-Idioms

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Idiom #223 for else loop

Loop through list items checking a condition. Do something else if no matches are found.

A typical use case is looping through a series of containers looking for one that matches a condition. If found, an item is inserted; otherwise, a new container is created.

These are mostly used as an inner nested loop, and in a location where refactoring inner logic into a separate function reduces clarity.

#include <list>
bool found = false;
for (const auto item : items) {
  if (item == "baz") {
    baz();
    found = true;
    break;
  }
}
if (!found) {
  DoSomethingElse();
}
#include <algorithm>
if (std::any_of(items.begin(), items.end(), condition))
    baz();
else
    DoSomethingElse();
using System.Linq;
if (!items.Any(i => MatchesCondition(i)))
{
	DoSomethingElse();
}
items := []string{"foo", "bar", "baz", "qux"}

for _, item := range items {
    if item == "baz" {
        fmt.Println("found it")
        goto forelse
    }
}
{
    fmt.Println("never found it")
}
forelse:
println(items.any { it == "baz" } ? 'found' : 'not found')

const found = items.some(condition);

if (!found) doSomethingElse();
items.find { it -> it == "baz" }?.let {
  println("found it")
} ?: println("never found it")
Found := False;
for Item in Items do
begin
  if Item.MatchesCondition then
  begin
    Found := True;
    Break;
  end;
end;
if not Found then 
  DoSomethingElse;
items = ['foo', 'bar', 'baz', 'qux']

for item in items:
    if item == 'baz':
        print('found it')
        break
else:
    print('never found it')
items = ['foo', 'bar', 'baz', 'qux']
puts items.any?("baz") ? "found it" : "never found it"
if let None = items.iter().find(|&&item| item == "rockstar programmer") {
        println!("NotFound");
    };
items
    .iter()
    .find(|&&item| item == "rockstar programmer")
    .or_else(|| {
        println!("NotFound");
        Some(&"rockstar programmer")
    });
let mut found = false;
for item in items {
    if item == &"baz" {
        println!("found it");
        found = true;
        break;
    }
}
if !found {
    println!("never found it");
}
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Idiom created by

Ruien

Related idioms

bool found = false;
for (const auto item : items) {
  if (item == "baz") {
    baz();
    found = true;
    break;
  }
}
if (!found) {
  DoSomethingElse();
}
if (std::any_of(items.begin(), items.end(), condition))
    baz();
else
    DoSomethingElse();
if (!items.Any(i => MatchesCondition(i)))
{
	DoSomethingElse();
}
items := []string{"foo", "bar", "baz", "qux"}

for _, item := range items {
    if item == "baz" {
        fmt.Println("found it")
        goto forelse
    }
}
{
    fmt.Println("never found it")
}
forelse:
println(items.any { it == "baz" } ? 'found' : 'not found')

const found = items.some(condition);

if (!found) doSomethingElse();
items.find { it -> it == "baz" }?.let {
  println("found it")
} ?: println("never found it")
Found := False;
for Item in Items do
begin
  if Item.MatchesCondition then
  begin
    Found := True;
    Break;
  end;
end;
if not Found then 
  DoSomethingElse;
items = ['foo', 'bar', 'baz', 'qux']

for item in items:
    if item == 'baz':
        print('found it')
        break
else:
    print('never found it')
items = ['foo', 'bar', 'baz', 'qux']
puts items.any?("baz") ? "found it" : "never found it"
if let None = items.iter().find(|&&item| item == "rockstar programmer") {
        println!("NotFound");
    };
items
    .iter()
    .find(|&&item| item == "rockstar programmer")
    .or_else(|| {
        println!("NotFound");
        Some(&"rockstar programmer")
    });
let mut found = false;
for item in items {
    if item == &"baz" {
        println!("found it");
        found = true;
        break;
    }
}
if !found {
    println!("never found it");
}