Set
 Usage
• lhs = rhs evaluates rhs and assigns the result to be the value of lhs. From then on, lhs is replaced by rhs whenever it appears.
• { ,  , ... } = { ,  , ... } evaluates the  , and assigns the results to be the values of the corresponding  .
Notes
• lhs can be any expression, including a pattern. • f[x_] = x^2 is a typical assignment for a pattern. Notice the presence of _ on the left-hand side, but not the right-hand side. • An assignment of the form f[args] = rhs sets up a transformation rule associated with the symbol f. • Different rules associated with a particular symbol are usually placed in the order that you give them. If a new rule that you give is determined to be more specific than existing rules, it is, however, placed before them. When the rules are used, they are tested in order. • New assignments with identical lhs overwrite old ones. • You can see all the assignments associated with a symbol f using ?f or Definition[f]. • If you make assignments for functions that have attributes like Flat and Orderless, you must make sure to set these attributes before you make assignments for the functions. • If lhs is of the form f[args], then args are evaluated. • When it appears in an unevaluated symbolic form, Set is treated as a scoping construct (see Section A.3.8). • lhs = rhs returns rhs even if for some reason the assignment specified cannot be performed. • Some global variables such as $RecursionLimit can only be assigned a certain range or class of values. • New in Version 1.
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