Function letrec

  • letrec<T>(
        builder: T extends Record<string, unknown>
            ? LetrecTypedBuilder<T<T>>
            : never,
    ): LetrecValue<T>

  • For mutually recursive types

    Type Parameters

    • T

    Parameters

    • builder: T extends Record<string, unknown> ? LetrecTypedBuilder<T<T>> : never

      Arbitraries builder based on themselves (through tie)

    Returns LetrecValue<T>

    Example

    type Leaf = number;
    type Node = [Tree, Tree];
    type Tree = Node | Leaf;
    const { tree } = fc.letrec<{ tree: Tree, node: Node, leaf: Leaf }>(tie => ({
      tree: fc.oneof({depthSize: 'small'}, tie('leaf'), tie('node')),
      node: fc.tuple(tie('tree'), tie('tree')),
      leaf: fc.nat()
    }));
    // tree is 50% of node, 50% of leaf
    // the ratio goes in favor of leaves as we go deeper in the tree (thanks to depthSize)

    Remarks

    Since 1.16.0

  • letrec<T>(builder: LetrecLooselyTypedBuilder<T>): LetrecValue<T>

  • For mutually recursive types

    Type Parameters

    • T

    Parameters

    Returns LetrecValue<T>

    Example

    const { tree } = fc.letrec(tie => ({
      tree: fc.oneof({depthSize: 'small'}, tie('leaf'), tie('node')),
      node: fc.tuple(tie('tree'), tie('tree')),
      leaf: fc.nat()
    }));
    // tree is 50% of node, 50% of leaf
    // the ratio goes in favor of leaves as we go deeper in the tree (thanks to depthSize)

    Remarks

    Since 1.16.0

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