Trains

Unlike in many other APLs, trains in TinyAPL are written using special syntax: ⦅, ⋄and ⦆. They are a sequence of arrays, functions, adverbs and conjunctions that combine to create functions or modifiers.

Note that, if a train has no diamonds, the contents are parsed with a special syntax where function application doesn't exist (but modifier application does), and then each tree becomes a tine. This means that, in most cases, you can omit diamonds in trains, making a Compact Train: ⦅+-×⦆ for ⦅+⋄-⋄×⦆ .

1-trains

The simplest train is the 1-train:

2-trains

3-trains

Longer trains

Longer trains are parsed right-to-left, two tines at a time, creating 3-trains; the result of an evaluation becomes the rightmost tine of the next group. If only a tine is left it is used to create a 2-train. If the left tine of a 3-train is empty, it becomes a 2-train, which can be useful to force a chain of functions to be an Atop instead of a Fork. To use an empty tine in a compact train, you can use the special token · instead.