Either

From Predicate

intermediate5 of 8

Learn about from predicate in fp-ts either

Code Editor

05-from-predicate.exercise.ts

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Test Results

Requirements

describe('validateAdult', () => {
  const adult: User = { id: 1, name: 'Alice', age: 25 }
  const minor: User = { id: 2, name: 'Bob', age: 16 }

  it('returns right for adult user', () => {
    const result = validateAdult(adult)
    expect(result).toEqual({ _tag: 'Right', right: { id: 1, name: 'Alice', age: 25 } })
  })

  it('returns left for minor user', () => {
    const result = validateAdult(minor)
    expect(result).toEqual({ _tag: 'Left', left: 'Must be 18 or older' })
  })
})
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Pro Tips

💡 Stuck? Here's what to try:

  • • Read the comments in the code carefully
  • • Run tests frequently to get feedback
  • • Check the fp-ts documentation
  • • Use the solution if you need help

🚀 Learning Approach:

  • • Focus on understanding, not just solving
  • • Experiment with different approaches
  • • Think about real-world applications
  • • Build on previous exercises