In teaching students to program with compositions of higher-order functions, we have encountered a sharp distinction in the difficulty of problems as perceived by students. This distinction especially matters as growing numbers of programmers learn about functional programming for data processing. We have made initial progress on identifying this distinction, which appears counter-intuitive to some. We describe the phenomenon, provide some preliminary evidence of the difference in difficulty, and suggest consequences for functional programming pedagogy.

@article{paperbot1494,
  title = {Structural versus pipeline composition of higher-order functions (experience report)},
  author = {Elijah Rivera and Shriram Krishnamurthi},
  journal = {Proceedings of the ACM on Programming Languages},
  volume = {6},
  number = {ICFP},
  year = {2022},
  doi = {10.1145/3547633}
}