Function letrec

For mutually recursive types

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)
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Remarks

Since 1.16.0

For mutually recursive types

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)
Copy

Remarks

Since 1.16.0