Having different variables under the same name, especially when we have to keep track of which is which (different values in different contexts, defined by inde

Having different variables under the same name, especially when we have to keep track of which is which (different values in different contexts, defined by indentation) does not sound like a good idea to me. For example, here's a problem I had in C when I used a local variable with the same name as a global variable: http://stackoverflow.com/questions/19214293/unable-to-modify-global-variable-in-c http://stackoverflow.com/questions/19214293/unable-to-modify... You're saying: "immutable things tends to be easier to reason about because names do not change what they refer to within a context" Can you please provide an example of that? Maybe some code where this 'feature' is useful? Your example of let x = 3 in print ((let x = 4 in x) + x) shows what you mean, but it does not show why would I want to do that. Thank you very much for your effort to help me understand.