Chains

Chains allow multiple expressions to be appended together.

Simple chains

A chain is written as a series of expressions delimited by arrows ->. The final expression determines the value of the chain as a whole.

-- This entire chain evaluates to 8, the result of the final expression.
2 + 5 -> cos [2] -> max [2, 4, 6, 8]

Forward passing

The key feature that makes chains useful is forward passing. This is when the result of the previous expression is used in the next expression.

The underscore _ name is reserved by Wolf. In a chain, it refers to the result of the previous expression.

-- The underscore is replaced with 4, so this whole chain evaluates to 14.
2 + 2 -> _ + 10

Automatic chaining

In some common cases, Wolf can infer where the first underscore goes.

For these cases, you can use the fat arrow => instead. This tells Wolf to insert the first underscore for you.

-- Manual:
[2, 5] -> max [_] -> log2 [_] -> ceil [_] -> exp2 [_]
2 -> _ + 5 -> _ * 3

-- Automatic:
[2, 5] => max => log2 => ceil => exp2
2 => + 5 => * 3

This feature works with:

• The single value passed to a function.
  • e.g. => my_func is rewritten as -> my_func [_]
• The .0 value passed to a function.
  • e.g. => my_func [a, b, c] is rewritten as -> my_func [_, a, b, c]
• The single value passed to a unary operator.
  • e.g. => - is rewritten as -> - _
• The left hand value passed to a binary operator.
  • e.g. => + a is rewritten as -> _ + a

You may mix thin arrows and fat arrows in the same chain.

[2, 5] => max -> 10 / _