Applicative style
Applicative style is a functional technique for combining independent computations through an applicative interface, including validation that accumulates errors rather than stopping at the first failure.
Functional Design and Architecture: Examples in Haskell
Applicative validation is a validation technique that combines independent checks while accumulating their errors rather than stopping at the first failure.
- How it is used
- Places validation between API input and domain logic so calculations receive only justified values.
- How deep it goes
- Defines applicative validation and demonstrates combinators, nested validators, and accumulated field errors.
- Examples
- Uses object-template fields, nested Inner and Outer records, pointed validators, and combined validation errors.
- What you can do after
- Apply applicative combinators in Haskell to validate independent fields and report multiple errors.
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Learn Haskell by Example
Applicative style is a functional programming style that combines independent computations using an applicative interface.
- How it is used
- Builds typed command-line configurations from independent option and argument parsers.
- How deep it goes
- Demonstrates parser primitives, applicative operators, metadata composition, execution, generated help, and nested configuration parsing.
- Examples
- Uses string, integer, Boolean, optional, synchronization-path, and verbosity arguments in executable CLI examples.
- What you can do after
- Apply it via Options.Applicative to build typed CLI parsers with validation, required-argument checks, help text, and version information.
Read how Learn Haskell by Example explains applicative style →
Related concepts
- optparse-applicativeused by · optparse-applicative is a Haskell library for declaratively defining and parsing command-line options and arguments.
- parseruses · A parser is a software component or algorithm that analyzes input according to a grammar or format to identify its structure, often producing a structured representation or reporting errors.
- pointed-validationimplemented by · pointed-validation is a Haskell library for applicative validation that records the location of errors within possibly hierarchical data structures.
- validationkind of · The process of checking data, behavior, systems, models, or results against defined criteria to assess their correctness, suitability, or acceptability.
- applicative functoruses · An applicative functor is an abstraction that applies functions within a computational context to context-wrapped values while combining their contexts.
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