ilusm

ilusm is a small programming language built around one idea:

write less, keep it readable, make it fun.

It is meant to be fast to type, easy to remember, friendly to use, and lighter on ceremony than most other languages. A lot of normal language baggage gets cut out or merged together so code stays short without turning into total symbol soup.

This repo is the reference implementation: lexer, parser, AST, and interpreter in Go.

It is my language, still in progress. What’s here is for my own build and dev workflow — not an open call for unsolicited changes or for treating the repo like a playground.

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Status

Work in progress.

Right now ilusm already has a real core:

• variables by first assignment
• short literals: tru, fls, nil
• one-line and block functions
• final-expression return
• if cond: a | b
• <- loops
• lists
• objects
• indexing
• dot access
• shorthand statement calls
• and, or, !

This is still early and the language may change while the core gets tightened.

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Goals

ilusm is trying to be:

• short
• readable
• fast
• fun
• friendly
• low ceremony

The rule is simple:

If something can be shorter, simpler, or combined with something else without making the language worse, it probably should be.

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Design vibe

A few big choices define the language:

Left out	Instead
let, var, const	assignment with =
func	function syntax without the keyword
braces	indentation blocks
semicolons	newlines
else	if a: b | c
for ... in ...	<-
mandatory return	final expression return

ilusm leans on:

• assignment by =
• final expression return
• indentation blocks
• |
• <-
• short builtins like prn

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Examples

Variables

x = 5
msg = "hello"
ok = tru
bad = fls
n = nil

Functions

add(a, b) = a + b

sum(xs) =
    s = 0
    x <- xs: s = s + x
    s

Conditionals

prn if ok: "yes" | "no"

Loops

x <- [1, 2, 3]: prn x
i <- 0..3: prn i

Objects

cfg = {ok: tru, prt: 8080}
prn cfg.prt

Logic

ok = tru
nick = nil
cfg = {ok: tru, prt: 8080}

prn ok and "yes"
prn nick or "guest"
prn cfg.ok and cfg.prt
prn !ok
prn if !ok: "no" | "yes"

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Syntax snapshot

Literals

tru
fls
nil
1
3.14
"txt"
[1, 2, 3]
{key: "ex", ok: tru}

Assignment

x = 1

Function

inc(x) = x + 1

sum(xs) =
    s = 0
    x <- xs: s = s + x
    s

Conditional

if ok: prn "yes" | prn "no"

msg = if ok: "yes" | "no"

Loop

x <- xs: prn x

Call

prn x
len xs
add(1, 2)
save()

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Builtins (so far)

The builtin surface is intentionally small:

Builtin	Role
prn	print
len	length
str	string
int	integer
typ	type

More can come later; the goal is to keep the core and stdlib small and sharp.

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Truthiness

Falsey: fls, nil, 0, "", []

Everything else is truthy.

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Range behavior

0..3 is inclusive on both ends — so 0..3 means 0, 1, 2, 3.

Descending ranges also work, e.g. 3..0.

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Rough edges

This is still early. Things work, but the language is not locked forever.

May still change: syntax details, parser rules, stdlib shape, runtime edge cases, what gets shortened further.

Already pretty central: tru / fls / nil, if a: b | c, <-, =, final-expression return, shorthand statement calls.

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Why this exists

Most languages make you type too much for small things. ilusm is an attempt to feel lighter and more direct without becoming unreadable or a novelty language.

The goal is not to be clever for its own sake. The goal is to make coding feel easier, faster, and a little more alive.

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Roadmap

Near-term ideas:

• interpolation
• field / index assignment
• more stdlib
• file running / CLI polish
• better errors
• more data handling
• maybe imports later, if deserved

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WIP note

This repo is active, unfinished, and still being shaped. If something looks strange, it may still be tested against the main rule:

Does this make the language simpler, faster, and better to use?

If yes, it stays. If not, it gets cut.

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Build from source

Requires Go 1.22 or newer. From the repo root:

go build -o ilusm ./cmd/ilusm

CLI:

./ilusm run path/to/script.ilu   # execute
./ilusm tok path/to/script.ilu   # tokens
./ilusm ast path/to/script.ilu   # AST
./ilusm run examples/demo.ilu

Layout:

Path	Role
cmd/ilusm	CLI
internal/lexer	tokenizer
internal/parser	parser
internal/ast	AST nodes
internal/runtime	interpreter
examples/	sample .ilu