Not all mappings are functions, Not all functions, one-one. Puppets controlled by Domain and Range, How on their threads, hang the fate of Functions I have just finished a set of 10 videos on the topic ‘Functions’ by following the new A level maths specification very closely. While primarily aimed at learners, it might make for a lesson plan for teachers of A level maths. Here is the first of the videos. I would love to hear from you about any suggestions or feedback.