Using C++ assert to check if a value exists

Question

How can I use c++ assert to check if a value is found in an array? I know I could use a simple for loop but I am supposed to use assert for my project.

Function signature:

template <class K, class V>
K& Map<K, V>::operator[](const V &value) const //Assert the argument is found 
//in the Values array and then return the key with the given value 
{
}

Update:

Is this code correct? I am not sure since it does not use assert to check if the value is found in an array.

template <class K, class V>
K& Map<K, V>::operator [] (const V &value) const
{
    for (int i = 0; i < size; i++) 
    {
        if (A2[i] == value)
            return A1[i];
    }

    assert(false);
}

Also, operator[] cannot be const if the Map works anything like std::map. — PaulMcKenzie
– PaulMcKenzie, Commented Nov 29, 2020 at 18:20
@PaulMcKenzie This operator[] will assert the key already exists, it is a precondition that the argument will be found. So it will not insert new elements and is not intended to behave like std::map. — François Andrieux
– François Andrieux, Commented Nov 29, 2020 at 18:22
using assert is no alternative to using a loop. You can do it with or without assert and with or without a (explicit) loop — 463035818_is_not_an_ai
– 463035818_is_not_an_ai, Commented Nov 29, 2020 at 18:23
"I know I could use a simple for loop but I am supposed to use assert for my project." assert is not a replacement for for here. You have to some how determine if value is in your map, then you can assert that condition. — François Andrieux
– François Andrieux, Commented Nov 29, 2020 at 18:24

Jarod42 · Accepted Answer · 2020-11-29 20:35:40Z

1

Is this code correct?

assert is "disabled" when NDEBUG is set. else std::abort would be called (after a diagnostic).

So, if code reaches that assert,

if NDEBUG is defined, your program reaches end of function returning non-void type, so it is undefined behavior.

If set, program is well defined and abort.

throwing exception might be more appropriated.

answered Nov 29, 2020 at 20:35

Jarod42

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