A friendly, fast programming language for people and their agents.
iyi is a compiled programming language written for two readers: the person editing the code and the agent editing it beside them. One rule serves both. A module builds against its dependencies' declarations, never their bodies, so:
- a build reads less
- a program carries less
- a model reads an interface instead of a repository
module app/greeter pub def polite(name : String) : String "Dear #{name}, welcome."▍ end
About 9x less, on the line you just changed.8.06x to 9.00x across 3 published sessions · the measurement
iyi is done. Crystal's rules are still reading bodies that did not change.
Edit one line, build. Both lanes start at the same moment.
Module names and the edit are illustrative. The two durations are the measured ones, from the same compiler binary under each set of rules, by a generator that refuses to start the clock until both print the same total.
What iyi is for
Four things, and they are one design decision seen from four sides.
Try iyi
It reads like Crystal or Ruby, and builds like a systems language. This is the first program of the tour, and the output beside it is what the compiler's build of it printed.
Run it in the playground →# Your first iyi program.
puts "Hello Türkiye!"Hello Türkiye!
Agent experience (AX)
A model reads the interface, not the repository.
A module compiles against its dependencies' declarations, never their bodies. That one rule is why a module's interface is a file, and why iyi mod context can hand an agent the exact surface of every import with no body in it and no repository behind it.
- Grounding is one command.
iyi mod context --jsonprints the surface an edit is allowed to know. - The verdict is data.
iyi check -f jsonanswers with the file, the line, the span and the exact replacement when the compiler knows the fix, andiyi fixapplies it. - The servers are in the binary.
iyi lspfor an editor andiyi mcpfor a harness, both over stdio.
Same fix. 31–43% fewer prompt tokens, for no fewer rounds.The recorded session →
Same four verbs in both lanes. Watch what each one has to read.
A replay of the measured result; the code in the lanes is illustrative. Rounds to green were the model's, tied three times and lost three. How it was measured.
Coming from Crystal?
iyi runs your Crystal code today.
iyi's compiler is Crystal's compiler. Your .cr files build unchanged, and iyi build --crystal gives an iyi program Crystal's standard library, require, and the shards you already depend on. Blocks, union types, nil-safety and macros are all here.
The listing is a Kemal server written as an iyi module, and the console under it is that server answering. What iyi adds is one rule about where things may be written, and the compiler teaches it as you go.
module site
require "kemal"
get "/" do |env|
"Hello from an iyi program"
end
get "/json" do |env|
env.response.content_type = "application/json"
{message: "iyi"}.to_json
end
Kemal.run$ iyi build --crystal -o site site.iyi $ ./site & $ curl localhost:3000/json {"message":"iyi"}
Install in one line
The latest release into ~/.local on Linux x86-64 or macOS arm64, or into %LOCALAPPDATA% on Windows x86-64, with both libraries and the samples. Then hello.
curl -fsSL https://raw.githubusercontent.com/iyilang/iyi/master/install.sh | sh ~/.local/bin/iyi run ~/.local/share/iyi/samples/hello.iyi
irm https://raw.githubusercontent.com/iyilang/iyi/master/install.ps1 | iex & "$env:LOCALAPPDATA\Programs\iyi\bin\iyi.exe" run "$env:LOCALAPPDATA\Programs\iyi\share\iyi\samples\hello.iyi"