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Programming-Idioms

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  • C++

Idiom #51 Check if map contains key

Determine whether the map m contains an entry for the key k

#include <map>
bool key_exists = m.find(k) != m.end();

m is a std::map. If value is not found, find returns end(), else it returns an iterator to the element.
#include <map>
bool key_exists = m.count(k) != 0;

Need C++14
#include <map>
bool key_exists = m.contains(k);

Need C++20
M.Contains (K)
New implementation...
< > ⌨
programming-idioms.org 
bool key_exists = m.find(k) != m.end();
bool key_exists = m.count(k) != 0;
bool key_exists = m.contains(k);
M.Contains (K)
(contains? m k)
bool keyExists = m.ContainsKey(key)
if (k in m) { }
m.containsKey(k)
Map.has_key?(m, k)
maps:is_key(K, M).
_, ok := m[k]
Map.member k m
(/=Nothing) (lookup k m)

_m.has(_k)
m.hasOwnProperty(k)
k in m
m.containsKey(k)
m.containsKey(k)
(nth-value 1 (gethash k m))
m[k] ~= nil
if (m[k]) ...
array_key_exists($k, $m)
m.IndexOf(k) >= 0
exists $m->{$k}
k in m
m.get(k)
m.has_key?(k)
m.key?(k)
m.include?(k)

m.contains_key(&k)
m.contains(k)
(assoc k m)
m includesKey: k.
If m.ContainsKey(k) Then...