Std.Num.sum

fn

This is a callable function.

What it does

Every element added together, or None for an empty collection.

None rather than the identity because a caller that wants nought for an

empty collection can say so, while one that needs to know it was empty

cannot get that back from a nought.

Read the signature

• The text after the name is the type checked by Pudu.
• Read arrows from left to right: inputs come first, and the final type is returned.
• & borrows a value for this call instead of moving or copying it.
• Names inside [ ] are type arguments, such as the item type held by a collection.
• Option holds Some(value) or None when no value is available.