tomo/docs/mutexed.md

Mutexed Data

To serve the general case of synchronizing access to shared datastructures, Tomo uses the mutexed keyword, which allocates a mutex and some heap memory for a value. Access to the heap-allocated value's memory can only be obtained by using a holding block. holding blocks ensure that the underlying mutex is locked before entering the block and unlocked before leaving it (even if a short-circuiting control flow statement like return or stop is used). Here is a simple example:

nums := mutexed [10, 20, 30]

>> nums
= mutexed [Int]<0x12345678> : mutexed([Int])

holding nums:
    # Inside this block, the type of `nums` is `&[Int]`
    >> nums
    = &[10, 20, 30] : &[Int]

thread := Thread.new(func():
    holding nums:
        nums:insert(30)
)

holding nums:
    nums:insert(40)
    
thread:join()

Without using a mutex, the code above could run into concurrency issues leading to data corruption.