Declarative programming is essentially programming through a parameter. The declaration is that parameter that will be passed to some instruction. In small dose

Declarative programming is essentially programming through a parameter. The declaration is that parameter that will be passed to some instruction. In small doses declarative programming occurs with every function call. In declarative programming the parameter is essentially the whole program and the instruction is implicit; we know more or less how it works, but generally assume it just exists or even forget about it and take it as the way things work. Of course declarative programming is simpler and less error prone. But it is also essentially inflexible. The implicit instruction is finite and will inevitably run into a situation when the baked execution logic does not quite fit. It will be either inefficient or require a verbose and repetitive parameter, or just flat out incapable of doing what is desired. In this case declarative programming fails; it is impossible to fix unless we rewrite the underlying instruction. E.g. 'printf' is a small example of declarative programming. It does work rather well, especially when the compiler is smart about type checks, but once you want to vary the text conditionally it fails. (The thing that replaces 'printf' are template engines that basically reimplement same logic and control statements you already have in any language and the engine works as an interpreter of that logic. The logic is rather crude and limited and the finer details of formatting are left to callbacks that are mostly procedural.) For example, how do I format a list so that I get "A" for 1, "A and A" for 2, and "A, A, and A" for more? Or how I format a number so that the thousand separator appears only if the number is greater than 9999? Or what to do if I have an UTF-8 output, but some strings I need to handle are UTF-16? The existing declarative way did not foresee these cases and to add them to the current model would complicate it substantially. But if I have a simple writer that writes basically numbers and strings I can very quickly write procedures for these specific cases. Instructions are primary by their nature. A piece of data on its own cannot do anything. It always has an implicit instruction that will handle it. So instructions are the things we have to master.