The Λ Language

Λ is the scripting language in document margins. It runs when a document is read.

Instructions

Instruction	Syntax	Effect
say	`say "text"`	Print. `{var}` substitution.
write	`write path "text"`	Append line to file
set	`set name "value"`	Set variable
set ←	`set name ← expr`	Set from expression
if	`if cond:`	Conditional (indented block)
loop	`loop:`	Infinite loop (indented block, 10K cap)
loop while	`loop while cond:`	Conditional loop (indented block)
inscribe	`inscribe path`	Create file (indented = content)
withdraw	`withdraw path`	Delete file
erode self	`erode self N`	Remove N lines from own Μ text
mutate self	`mutate self "old" "new"`	Replace text in own Μ layer
wait	`wait Ns`	Pause N seconds

Expressions

Expression	Returns
`count path/*`	Number of items in directory
`read-count`	Times this document was read
`random-line path`	Random line from a file (xorshift PRNG)
`random-choice path/`	Random filename from directory
`ask "prompt"`	Reader's typed input

Conditions

Form	True when
`var > N`	Greater than
`var < N`	Less than
`var == "text"`	Equals
`var`	Non-empty, not "0"

Built-in variables

Variable	Contains
`{reader}`	Username
`{time}`	HH:MM:SS
`{date}`	YYYY-MM-DD
`{documents-read}`	Session count
`{read-count}`	This document's read count
`{document}`	This document's name

Self-modification

Documents can modify their own Μ (text) layer:

erode self N removes N lines from the end of the visible text. The Λ layer survives after the text is gone.
mutate self "old" "new" replaces the first occurrence in the text. The document rewrites itself.

Both operations preserve the --- Λ --- separator. The logic layer is never eroded.

The grid language

Beneath simple Λ is the full ΦΜΛ grid language — a two-dimensional esoteric programming language. Grid programs use inspect -deep to view. Simple Λ instructions compile conceptually down to grid operations, but you never need to touch the grid unless you want to.

Example


A greeting that remembers you.

--- Λ ---
set visits ← read-count
if visits == "1":
  say "Welcome, {reader}. First visit."
if visits > 1:
  say "Welcome back. Visit #{visits}."
set mood ← ask "How are you?"
say "Noted: {reader} is {mood}."
write west-wing/journal/{date} "{time} {reader}: {mood}"

Example with loop


A countdown timer.

--- Λ ---
set n "10"
loop while n > 0:
  say "{n}..."
  set n ← n - 1
  wait 1s
say "Done."