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Set Command

rascal-0.41.2

Synopsis​

Set parameters that control options of RascalShell.

Syntax​

  • :set
  • :set Option TrueOrFalse

Description​

The shell provides a number of options to control its behaviour. The set command manages their value.

In the first form, the list of current settings is printed.

In the second form a specific option is set to true or false.

The options are:

  • profiling: record execution times while executing subsequent Rascal code and print the results after each RascalShell command.
  • tracing: while executing Rascal code, print a trace of all function calls.
  • errors: print more diagnostic stack traces if available (of internal functionality)

Examples​

Turn tracing on and execute a function:

rascal>import List;
ok
rascal>:set tracing true
ok
rascal>index(["a","b","c"])
call  >List::index(["a","b","c"])
call  >>List::size(["a","b","c"])
return>>>List::size:3
call  >>List::upTill(3)
return>>>List::upTill:[0,1,2]
return>>List::index:[0,1,2]
list[int]: [0,1,2]

Turn trace off and execute the same function:

rascal>:set tracing false
ok
rascal>index(["a","b","c"])
list[int]: [0,1,2]

Benefits​

  • profiling provides an accurate and non-invasive profile using a stack sampling method. With high probability the operations that appear to be taking the most time are indeed a bottleneck.
  • tracing is helpful to see which of the overloaded functions have been called and what their result was.

Pitfalls​

  • The set command is completely unrelated to Rascal's built-in set type.
  • tracing is expensive because of the high amount of IO it generates. Better use with care on small examples.
  • profiling gives insight into the Rascal program's behavior but not necessarily in the underlying cost of interpreting a Rascal program.
  • errors is a window into the implementation of Rascal rather than the notion of Rascal programs as they run. It is used for developers of the compiler and interpreter.