Block operations

[ahdinosaur]

• $if: pull/7
• $let: pull/8
• $type
• $switch: issues/47
• $switchAll: issues/48
• $map:
• MapObject
• Filter
• Flatten
• FlattenDeep
• Merge
• MergeDeep
• Sort
• Reverse

What other block operations might we want or need?

[ahdinosaur]

am thinking about Map, and other cases where variables are defined inline.

rather than:

$map: [2, 4, 6]
each(x):
  $eval: x + a

i wonder if we defined the variables more similar to Let.

$map: [2, 4, 6]
let: [x]
each:
  $eval: x + a

because this will be easier to parse with serde and give us extra space for possibly adding new features like functions and type checking.

at the same time, maybe not necessary.