Cookbook

Cookbook

Copy-paste patterns. Each is complete and doctested elsewhere — start here, then follow the link.

Validate input, keep partial results — and update every row§

Validate a payload into a typed value; sum the valid ones and skip the bad ones with try/recover. Then change every row of a table: lists and maps are values, so each r in rows + set r[…] would only change the loop's copy. Build the new rows with apply + merge, give them back, and set rows to … in the caller:

-- Doc cookbook: validate a payload into a typed value, and sum valid ones with
-- partial results (try/recover skips the bad ones); then update every row of a
-- table the value-semantics way. Copy-paste-ready patterns.
intent: "doc cookbook: validate + partial results + update rows"

type Order
    id: number
    total: number

task validate_order(payload)
    when "total" not in payload
        raise("missing total")
    when payload["total"] < 0
        raise("total must be >= 0")
    give Order(payload["id"], payload["total"])

task bad_order()
    give validate_order({"id": 2, "total": -5})

task safe_total(payloads)
    let total be 0
    each p in payloads
        try
            let o be validate_order(p)
            set total to total + (total of o)
        recover err
            log "skipped: " + err          -- partial results: skip the invalid ones
    give total

-- Lists and maps are values: `each r in rows` + `set r[...]` would change a copy.
-- Build the new rows and give them back.
task with_discount(rows, pct)
    give apply((r) => merge(r, {"total": r["total"] * (100 - pct) // 100}), rows)

print("safe_total of mixed orders → " + text(safe_total([{"id": 1, "total": 10}, {"id": 2, "total": -1}, {"id": 3, "total": 5}])))

test "validate accepts good input and rejects bad"
    assert_eq(total of validate_order({"id": 1, "total": 100}), 100)
    assert_error(bad_order)
    assert_error(() => validate_order({"id": 3}))

test "partial results: invalid orders are skipped"
    assert_eq(safe_total([{"id": 1, "total": 10}, {"id": 2, "total": -1}, {"id": 3, "total": 5}]), 15)

test "update every row: build new rows, the original stays as it was"
    let rows be [{"id": 1, "total": 200}, {"id": 2, "total": 50}]
    let cheaper be with_discount(rows, 10)
    assert_eq(cheaper, [{"id": 1, "total": 180}, {"id": 2, "total": 45}])
    assert_eq(rows[0]["total"], 200)
    set rows to with_discount(rows, 10)
    assert_eq(rows, cheaper)

The other patterns (each fully shown on its page)§

• A styled page from a layout + components — { layout }, named slots, { include … with {props} }, inline CSS in a { raw } block → Build a website.
• A classic form (no JS) — <form method="post"> + form of request (urlencoded/multipart, file uploads as exact bytes) → Build a website.
• Custom 404/500 pages with honest statuses — errors with <task>; HTML for browsers, JSON for agents, redirect for a 401 → HTTP server.
• Safe data into an inline <script> — { raw json_for_script(x) } (never json_encode there) → Frontend.
• Routes split into modules — export routes + mount alias.group at "/prefix" → Modules.
• HTTP API with auth + validation — auth with, expect body {…}, the response helpers → HTTP server.
• CRUD over SQL — db_open / sql_exec / sql (SQLite in-memory in the doctest) → SQL, Mongo & Redis.
• One LLM operation — generate "…" given X, branch on llm_available() → LLM primitives.
• An agent with tools — the llm_step + call_tool allow-list loop → Tool calling.
• A secret in any header — {"x-api-key": secret("KEY")} / bearer(...), materialized only at the socket → Secrets.
• Read/write a file with capabilities — require file(...) + read_file/write_file → Files & I/O.
• The on-chain loop — read (nonce/fees/UTXOs) → build → confirm the numbers → sign (the one gated door) → send → bounded wait; EVM (incl. Base/Arbitrum/Optimism L2s) → Blockchain, Bitcoin (every satoshi accounted for) → Bitcoin.
• Cold custody with PSBT — the agent prepares and audits, a human signs on their hardware wallet, the agent finalizes and broadcasts (the key never touches the agent's machine) → Bitcoin.
• A fund transfer behind a human gate — confirm "… fee X?" within 15m BEFORE secp256k1_sign, composed under serve with cron monitoring and a negotiated chart() → Blockchain (the flagship route).
• Thousands of live feeds in one thread — the while + ws_select event loop, opt-in reconnect + keepalive, parallel_map fan-out → WebSocket.

Every snippet on those pages is doctested against this version, so an LLM can copy one and it works.