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Programming-Idioms

  • JS
  • C++

Idiom #52 Check if map contains value

Determine whether the map m contains an entry with the value v, for some key.

Is this value contained in this map, for any key? 
#include <algorithm>
std::find_if(m.begin(), m.end(), [v](const auto& mo) {return mo.second == v; }) != m.end();

c++ 14

A lambda expression is used because built-in functions would search by key, not by value.
Object.values(m).includes(v)

JavaScript objects are hashmaps.
Object.values() converts a hashmap to a list of values.
Array#includes then checks whether v is included.
[...m.values()].includes(v)

Unlike the previous implementation, this works for Map objects rather than normal Objects.
(boolean (some #{v} (vals m)))

In Clojure values are truthy/falsy

no need for boolean, however included due to other language examples
New implementation...
< > ⌨
programming-idioms.org 
std::find_if(m.begin(), m.end(), [v](const auto& mo) {return mo.second == v; }) != m.end();
Object.values(m).includes(v)
[...m.values()].includes(v)
(boolean (some #{v} (vals m)))
m.ContainsValue(v)
m.byValue.canFind(v);
m.containsValue(v);
Map.values(m) |> Enum.member?(v)
func containsValue[M ~map[K]V, K, V comparable](m M, v V) bool {
	for _, x := range m {
		if x == v {
			return true
		}
	}
	return false
}
func containsValue(m map[K]T, v T) bool {
	for _, x := range m {
		if x == v {
			return true
		}
	}
	return false
}
elem v (elems m)

m.containsValue(v)
m.containsValue(v)
in_array($v, $m, true);
m.IndexOfData(v) >= 0
print "Found it!" if exists $m{$v};
v in m.values()
def k(x, m):
    for k, v in m.items():
        if v == x: return k
k = k(v, m)
x = False
for y in m.items():
    if y[1] == v:
        x = y[0]
        break
m.value?(v)
let does_contain = m.values().any(|&val| *val == v);
m.valuesIterator.contains(v)
m includes: v.