basic.nix

Source: /nix/store/mls72plk3raskl1r5afh3cl9ik3rn969-source/nix/basic.nix

Module Description

Basic effect constructors for lifting values

Combinators

pure

Creates a pure (effect-free) value with no context requirements.

This is the simplest way to lift a plain value into the effect system. The resulting effect is immediately available and requires no context. Equivalent to immediate {}.

Type Signature

V -> Fx<{}, V>

Parameters

• value: Any value to wrap in an effect

Example

pure 42           # => Fx<{}, Int>
pure "hello"      # => Fx<{}, String>
runFx (pure 42)    # => 42

See Also

• value - Similar but preserves any context type
• immediate - Lower-level constructor used internally

value

Creates an effect that produces a value while preserving any context.

Unlike pure which requires empty context, value works polymorphically over any context type. The context passes through unchanged.

Type Signature

V -> Fx<S, V> (for any S)

Parameters

• v: The value to produce

Example

# Works in any context
provide { x = 1; } (value 42)  # => 42

# Useful in sequencing when you need a constant
mapM (x: value (x * 2)) someEffect

See Also

• pure - When you know context is empty
• func - When value depends on state

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