This is back to the usual intractable problem - naming things. If you name the function properly and it abstracts the operation of the function precisely then y

This is back to the usual intractable problem - naming things. If you name the function properly and it abstracts the operation of the function precisely then you have added information, not taken it away. You understand what 'has_kettle_boiled' means. Inlining functions makes it difficult in a sequence to work out what are the separate steps. Splitting those out into a function - particularly if they take the temporary variables with them - makes it easier to understand what the higher level function does, not harder. Perhaps we should revisit stepwise refinement as a technique and the need for functions to be loosely coupled and highly cohesive.