Tuesday Coding Tip 11 — null-coalescing operator

Question

Tuesday coding tips are super short posts about various tidbits mainly from C++, but also from other programming languages I use. You can also follow the #TuesdayCodingTips hashtag on Mastodon and Linkedin.

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Some languages, like C# or Javascript, have a special operator ?? which is a specialization over the normal ternary operator. It either returns the value of the left operand or, if it is null, it returns the value of the right operand.

Furthermore, the ??= operator allows you to only assign to a variable if it is null. Syntax among languages might differ, so check out this overview: https://en.wikipedia.org/wiki/Null_coalescing_operator

var a = null;

// Initialize b with a, or with 42 if a is null
var b;
if (a == null) b = 42;
else b = a;

// Shorter version with ?? operator
var c = a ?? 42;

// Update a with something if it is null
a ??= 24;