Wolfram Language & System 10.0 (2014)|Legacy Documentation
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switches on a message, so that it can be printed.
switches on a named group of messages.
switches on tracing for the symbol s.
switches on several messages or message groups.
- Some messages for built-in functions are off by default, and must explicitly be switched on using On.
- In On["name"], possible named message groups include:
"Compiler" warnings associated with compiled code "Graphics" warnings associated with graphics generation "Packing" notifications associated with packed arrays "Spelling" spell-checking messages for symbol names "Symbolics" warnings associated with symbolic computation
- $MessageGroups gives a complete list of message groups recognized by On.
- On[General::name] switches on all messages derived from General::name.
- When tracing is switched on, each evaluation of a symbol, on its own or as a function, is printed, together with the result.
- Note that the tracing information is printed when a function returns. As a result, traces of recursive functions appear in the opposite order from their calls.
- On[Assert] switches on messages associated with assertions specified by Assert.
- On[s] is equivalent to On[s::trace].
- On is equivalent to On[s::trace] for all symbols.
Introduced in 1988
(1.0)| Updated in 2010