Have you read Backus' original FP paper "Can programming be liberated from the von Neumann style?: a functional style and its algebra of programs"? https://dl.

Have you read Backus' original FP paper "Can programming be liberated from the von Neumann style?: a functional style and its algebra of programs"? https://dl.acm.org/doi/10.1145/359576.359579 https://dl.acm.org/doi/10.1145/359576.359579