Roc rewrites the compiler in Zig(gist.github.com)

    //typical implementation
    const howManyAdults = (data) => {
      const adults = data
        .flatMap(obj => obj.type === 'parent' ? [obj, ...obj.children] : obj)
        .filter(obj => typeof obj.age === 'number')
        .filter(obj => obj.age >= 18 && obj.age < 150)

      adults.forEach(adult =>
        console.log(`${adult.name} is an adult age ${adult.age}`)
      )

      return adults.length
    }


    //nice "point-free" implementation using helper functions
    const transformData = obj => obj.type === 'parent' ? [obj, ...obj.children] : [obj]
    const isAdult = obj => obj.age >= 18 && obj.age < 130

    const howManyAdults = pipe(
      flatMap(transformData),
      filter(hasTypeOf('age', 'number'),
      filter(isAdult),
      logEach`${pick('name')} is an adult age ${pick('age')}`,
      len,
    )


    //completely point-free gets crazy
    const howManyAdults = pipe(
      flatMap(ifElse(
        compose(eq('parent'), pick('type')), 
        juxt([identity, pick('children']),
        identity,
      ), []),
      filter(hasTypeOf('age', 'number'),
      filter(both(gte(pick('age',18), lt(pick('age'), 130)))),
      logEach`${pick('name')} is an adult age ${pick('age')}`,
      len,
    )