Synchronization variables (also often called dataflow variables in the literature) are variables that can be written only once; attempts to read the variable block until it has been written to.
Synchronization variables are created with CreateSyncVar (9.1-1), written with SyncWrite (9.1-2) and read with SyncRead (9.1-3).
gap> sv := CreateSyncVar();; gap> RunAsyncTask(function() > Sleep(10); > SyncWrite(sv, MakeImmutable([1, 2, 3])); > end);; gap> SyncRead(sv); [ 1, 2, 3 ]
‣ CreateSyncVar( ) | ( function ) |
The function CreateSyncVar takes no arguments. It returns a new synchronization variable. There is no need to deallocate it; the garbage collector will free the memory and all related resources when it is no longer accessible.
‣ SyncWrite( syncvar, obj ) | ( function ) |
SyncWrite attempts to assign the value obj to syncvar. If syncvar has been previously assigned a value, the call will fail with a runtime error; otherwise, obj will be assigned to syncvar.
In order to make sure that the recipient can read the result, the obj argument should not be a thread-local object; it should be public, read-only, or shared.
‣ SyncRead( syncvar ) | ( function ) |
SyncRead reads the value previously assigned to syncvar with SyncWrite (9.1-2). If no value has been assigned yet, it blocks. It returns the assigned value.
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