Intercepting the Creation of New Symbols
Mathematica creates a new symbol when you first enter a particular name. Sometimes it is useful to "intercept" the process of creating a new symbol.
Mathematica provides several ways to do this.
| On[General::newsym] | print a message whenever a new symbol is created |
| Off[General::newsym] | switch off the message printed when new symbols are created |
Printing a message when new symbols are created.
This tells Mathematica to print a message whenever a new symbol is created. |
Mathematica now prints a message about each new symbol that it creates.
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This switches off the message. |
Generating a message when
Mathematica creates a new symbol is often a good way to catch typing mistakes.
Mathematica itself cannot tell the difference between an intentionally new name, and a misspelling of a name it already knows. But by reporting all new names it encounters,
Mathematica allows you to see whether any of them are mistakes.
| $NewSymbol | a function to be applied to the name and context of new symbols which are created |
Performing operations when new symbols are created.
When
Mathematica creates a new symbol, you may want it not just to print a message, but instead to perform some other action. Any function you specify as the value of the global variable
$NewSymbol will automatically be applied to strings giving the name and context of each new symbol that
Mathematica creates.
This defines a function to be applied to each new symbol which is created.
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The function is applied once to v and once to w.
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