Display an execution trace for

  • a point of execution or
  • an expression or expressionlist or
  • all args and locals in the current method

or enable or disable subsequent trace output.

Tracing an expression or expressionlist is unlike a print of the same expression in that

  • The display format is different; trace generates expression-text = expression-value for each expression
  • Position information (filename, line number, declaring class and method) of the trace line is printed
  • Traces can be suppressed on a build by a cobra commandline argument

cobra -include-traces:no ...

traces are useful for debugging (displaying interim expression values) and logging a point of execution( e.g. indicating that code in a code block is being executed).

A simple trace' statement with no arguments gives just the position info of the trace statement - the filename, line number, declaring class name and declaring method name that the trace is located in.
If the current object's class is a subclass of the declaring class then the subclass name is reported as well.

When given one or more expressions, trace gives the same information plus the source code and value of each expression.

The trace all statement is a convenience for logging

  • this,
  • every method argument and
  • every local variable.

The trace off statement turns off the subsequent trace statements in the declaring method.

The trace on statement turns them back on.


trace <expr1>, <expr2>, ... <expr3>
trace all
trace off
trace on


class Foo 

    var _z as int 

    def computeStuff(x as int, y as int) 
        if x > y 
        _z = x * y 
        trace all 
        trace _z

trace: at Foo.cobra:7; in Foo.computeStuff
trace: this=Foo; x=4; y=2; at Foo.cobra:10; in Foo.computeStuff
trace: this=Foo; _z=8; at Foo.cobra:11; in Foo.computeStuff


Needs a way to display just the expression (suppress position info).

See also  manual: trace statement documentation