A CAS operation includes three operands — a memory location (v), the expected old value (a), and a new value (B).
CAS操作包含三个操作数——内存位置(V)、预期原值(A)和新值(B)。
2
The call to map walks through each value, aliases it to v: val, evaluates the expression in the string, and replaces the value with the result of that expression.