gistfile1.lua

std = std or {}
std.runtime = std.runtime or {}

std.runtime.queue = {}

function std.runtime.schedule(coro, value)
    table.insert(std.runtime.queue, { coro = coro, value = value })
end

local Channel = { }
function std.runtime.newChannel()
    result = {
        senders = {},
        receivers = {},
    }
    setmetatable(result, { __index = Channel })
    return result
end

function Channel:send(value)
    local coro = coroutine.running()
    if #self.receivers > 0 then
        local receiver = table.remove(self.receivers, 1)
        receiver(value)
        std.runtime.schedule(coro)
    else
        table.insert(self.senders, function()
            std.runtime.schedule(coro)
            return value
        end)
    end
    coroutine.yield()
end

function Channel:receive(value)
    local coro = coroutine.running()
    if #self.senders > 0 then
        local sender = table.remove(self.senders, 1)
        local value = sender()
        std.runtime.schedule(coro, value)
    else
        table.insert(self.receivers, function(x)
            std.runtime.schedule(coro, x)
        end)
    end
    return coroutine.yield()
end

function std.runtime.spawn(f)
    local coro = coroutine.create(function()
        return f()
    end)
    std.runtime.schedule(coro)
end

local c = std.runtime.newChannel()

std.runtime.spawn(function()
    print('A: sending 42')
    c:send(42)
    print('A: sent 42')
end)

std.runtime.spawn(function()
    print('B: receiving')
    local value = c:receive()
    print('B: received ' .. value)
end)

while #std.runtime.queue > 0 do
    local entry = table.remove(std.runtime.queue, 1)
    coroutine.resume(entry.coro, entry.value)
end