local function identity(x) return x end

local TYPES = {
    ln = {
        -- inputs to the operation
        argc = 1,
        -- bounds on inputs
        min = {0.01},
        max = {1000},
        -- how to present the problem (for string.format)
        disp = "ln(%.2f)",
        -- transform input to output
        func = math.log,
        -- check guess g to canonical answer c
        good = function(c, g) return math.abs(c - g) < 0.05 end,
        -- transform range [0, 1) to a good distribution
        bias = function(r) return r^2 end,
    },
}

-- ideally, configure these parameters with options/inputs
local COUNT = 10
local TYPE = TYPES.ln
local TRIES = 1
local TIME = 3

local sc = 0
local oc = 0
for i = 1,COUNT do
    local rarg = {}
    for j = 1,TYPE.argc do
        table.insert(rarg, TYPE.min[j] + (TYPE.max[j] - TYPE.min[j]) * (TYPE.bias or identity)(math.random()))
    end
    local ans = TYPE.func(table.unpack(rarg))
    io.write(string.format(TYPE.disp .. " ? ", table.unpack(rarg)))
    io.flush()
    local st = os.time()
    local inp
    local fails = 0
    while os.time() - st < TIME do
        inp = tonumber(io.read("l")) or 0
        if os.time() - st > TIME then
            if TYPE.good(ans, inp) then
                oc = oc + 1
            end
            io.write(string.format("too slow! (%.2f)\n", ans))
        elseif TYPE.good(ans, inp) then
            io.write("✓ correct\n")
            sc = sc + 1
            break
        elseif fails < TRIES then
            io.write("wrong, try again ")
            io.flush()
            fails = fails + 1
        else
            io.write(string.format("wrong (%.2f)\n", ans))
            break
        end
    end
end
io.write(string.format("%d/%d correct, of which %d were too slow\n", (sc + oc), COUNT, oc))