↰ base.iter.IterMapper[E:imm,mut,read,R:imm,mut,read]

• base.iter.Iter/1
• base.iter.IterFolder/2
• base.iter.IterForEacher/1
• base.iter.IterMapper/2
• base.iter.IterPredicate/1
• base.iter.IterScanner/3
• base.iter.Sum/0

mut .some(x: E): mut base.Opt[R] -> …, // from base.OptMap/2
mut .empty: mut base.Opt[R] -> …, // from base.OptMap/2
mut #(t: E): R, // from base.OptMap/2