---
title: 'Higher-order and modular programming'
part: 'Part III — The Language'
partNumber: 3
order: 8
subtitle: '@name, closures, map/filter/reduce, import/export, and the module linker'
---

_Content coming soon._ This chapter connects first-class procedure references and closures to
`map`, `filter`, `reduce`, `bind`, and `compose`, then introduces `import`/`export` and the
bundled `std.*` module namespace used throughout Part IX.

<Run>{`// A closure remembers the radius it was configured with
def ringof(r) [
  return def(p) [ return vdist(p, [0, 0]) < r ]
]
let inside = ringof(20)
print map([[0, 0], [10, 10], [30, 0]], inside)`}</Run>

<Checkpoint chapterId="ch-20">Chapter content coming soon.</Checkpoint>