Local functions in C#

Functions can live inside the body that uses them.

// local functions live inside the surrounding body
int Square(int x) => x * x;

int SumOfSquares(int[] values)
{
    var total = 0;
    foreach (var v in values) total += Square(v);
    return total;
}

var data = new[] { 1, 2, 3, 4 };
Console.WriteLine(Square(9));
Console.WriteLine(SumOfSquares(data));

How it works

1. int Square(int x) => x * x; declares one locally, expression-bodied.
2. SumOfSquares calls its sibling; nothing leaks outside the file.
3. In a top-level program this is the shortest path to a helper.

Keywords and builtins used here

• Square
• SumOfSquares
• foreach
• in
• int
• new
• return
• var

The run, in numbers

Lines

13

Characters to type

293

Tokens

80

Three-star pace

90 tpm

At the three-star pace of 90 tokens a minute, this run takes about 53 seconds.

Type this snippet

Step 2 of 3 in Methods, step 16 of 29 in Language basics.

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