This is a Pony reimplementation of the C example from the SQLite quickstart page (http://sqlite.org/quickstart.html), using Pony's FFI system (http://tutorial.ponylang.org/c-ffi/calling-c/). In writing it I found a bug in Pony (which was subsequently fixed), so the exercise was good for something other than just learning. I'm still learning Pony…

sqlite-in-5-minutes.pony

use "collections"
use "lib:sqlite3"

actor Main
  let _env: Env
  new create(env: Env) =>
    _env = env
    let args = env.args

    var db: Pointer[U8] = Pointer[U8]
    var zErrMsg: Pointer[U8] = Pointer[U8]
    var rc: I32 = 0
    let prog = try
      args(0)
    else
      _env.err.print("There's no 0th argument, I don't know how you got here.")
      _env.exitcode(1)
      return
    end

    if (args.size() != 3) then
      _env.err.print(recover String().append("Usage: ").append(prog).append(" DATABASE SQL-STATEMENT") end)
      _env.exitcode(1)
      return
    end

    (let database, let sql) = try
      (args(1), args(2))
    else
      ("", "")
    end

    rc = @sqlite3_open[I32](database.cstring(), addressof db)

    if (rc != 0) then
      let errMsg = String.from_cstring(@sqlite3_errmsg[Pointer[U8]](db))
      let msg = String().append("Can't open database: ").append(errMsg)
      _env.err.print(msg.clone())
      @sqlite3_close[None](db)
      _env.exitcode(1)
      return
    end

    rc = @sqlite3_exec[I32](db, sql.cstring(), addressof this.callback, this, addressof zErrMsg)

    if (rc != 0) then
      let errMsg = String.from_cstring(zErrMsg)
      let msg = String().append("SQL error: ").append(errMsg)
      _env.err.print(msg.clone())
      @sqlite3_free[None](zErrMsg)
    end

    @sqlite3_close[None](db)

  fun iso callback(argc: I32, argv: Pointer[Pointer[U8]], azColName: Pointer[Pointer[U8]]): I32 =>
    let args = Array[Pointer[U8]].from_cstring(argv, USize.from[I32](argc))
    let colNames = Array[Pointer[U8]].from_cstring(azColName, USize.from[I32](argc))

    for i in Range[USize](0, USize.from[I32](argc)) do
      try
        let arg = String.from_cstring(args(i))
        let columnName = String.from_cstring(colNames(i))
        _env.out.print(" = ".join([columnName, arg]))
      end
      _env.out.print("")
    end
    I32(0)

What was the bug, can you link to the issue?