constant(value)

This returns a deep map-based tree that has the indicated value for any requested leaf node.

// constant.ori
Tree.constant(1)

This always returns the value 1 for any path to a leaf node:

$ ori constant.ori/a
1
$ ori constant.ori/b
1
$ ori constant.ori/a/b/c
1

Set a default value #

One use for constant is to define a default value for a tree using Tree.deepMerge.

// deepDefault.ori
Tree.deepMerge(
  Tree.constant(0) // Default value is zero
  {
    a: 1
    b: {
      c: 2
    }
  }
)

This provides the default value of zero for any level of the tree:

$ ori deepDefault.ori/a
1
$ ori deepDefault.ori/x
0
$ ori deepDefault.ori/b/c
2
$ ori deepDefault.ori/b/y
0