• I am not a maths I am a code. I make no claims to validity of the math with in.

This prediction market uses the Liquidity-Sensitive Logarithmic Market Scoring Rule (LS-LMSR) to price YES/NO outcome shares. The system is structured in three layers:

• lib: Pure Rust library implementing LS-LMSR math and engine
• server: HTTP interface exposing market actions (buy, sell, price, simulate)
• client: HTML/JS interface for interacting with the server

start the http server, that also serves a UI at :8000/

cargo run -p lslmsr-server

flowchart TD
    A[HTML Client] -->|HTTP/JSON| B[Tiny HTTP Server]
    B -->|Calls into| C[LS-LMSR lib]
    C --> D[Market Engine]
    C --> E[Fixed-Point Math Utils]

• lslmsr.rs: Implements cost/pricing logic
• market.rs: Market state and trade logic
• types.rs: Share structs, enums, errors
• Uses u128 fixed-point math (1e18 scale)

• Routes:

  • GET /price
  • POST /buy
  • POST /sell
  • POST /simulate

• Wraps a MarketEngine in a shared Arc<Mutex<...>>

• HTML/JS frontend
• Fetches data, renders prices, allows trade submission

sequenceDiagram
    participant U as User (Browser)
    participant C as Client (HTML/JS)
    participant S as Server (Rust HTTP)
    participant L as LS-LMSR lib

    U->>C: Clicks "Buy YES"
    C->>S: POST /buy { outcome: "YES", amount: "100e18" }
    S->>L: market.buy("YES", 100e18)
    L->>L: Calculates b = alpha * sqrt(total shares)
    L->>L: Calculates new cost
    L->>L: Mints YES shares, updates state
    L-->>S: Result: OK, new price
    S-->>C: JSON response
    C-->>U: Show confirmation, updated prices

b = alpha * sqrt(q_yes + q_no)

C(q) = b * ln(e^(q_yes/b) + e^(q_no/b))
Price(YES) = e^(q_yes/b) / (e^(q_yes/b) + e^(q_no/b))

Values handled in u128 with 18 decimals (fixed-point math).

{
  "outcome": "YES",
  "amount": "100000000000000000000"
}

{
  "success": true,
  "new_price": {
    "yes": "0.540000000000000000",
    "no": "0.460000000000000000"
  }
}

curl http://localhost:8000/price

curl -X POST http://localhost:8000/simulate \
  -H "Content-Type: application/json" \
  -d '{"outcome": "YES", "amount": "1000000000000000000"}'

curl -X POST http://localhost:8000/buy \
  -H "Content-Type: application/json" \
  -d '{"outcome": "YES", "amount": "1000000000000000000"}'

curl -X POST http://localhost:8000/sell \
  -H "Content-Type: application/json" \
  -d '{"outcome": "YES", "amount": "1000000000000000000"}'