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Introduction to Debugging

The Maxima has source level capabilities. We can set a breakpoint at a line in a file, and then step line by line from there. The call stack may be examined, together with the variables bound at that level.

The ideal way to run Maxima is using dbl mode in GNU emacs. Then when we break in a function, the source code auto magically appears in the other window. One can step line by line, seeing a little arrow in the other window, indicating where you are. As you go up the call stack, the other window changes showing where you were inside that function. Even if you do not use the debugger, it is convenient to be able to evaluate forms directly from your source file into the inferior maxima.

To do all this in emacs type

M-x dbl

This will give you a window, and then you invoke maxima as you usually would. Look at the Mode help (c-h m) in emacs to get more information.

Maxima now allows special commands beginning with a ':'. This was introduced because of the debugger.

Definitions for Debugging

Variable: REFCHECK
default: [FALSE] - if TRUE causes a message to be printed each time a bound variable is used for the first time in a computation.

Function: REMTRACE ()
This function is no longer used with the new TRACE package.

Variable: SETCHECK
default: [FALSE] - if set to a list of variables (which can be subscripted) will cause a printout whenever the variables, or subscripted occurrences of them, are bound (with : or :: or function argument binding). The printout consists of the variable and the value it is bound to. SETCHECK may be set to ALL or TRUE thereby including all variables. Note: No printout is generated when a SETCHECKed variable is set to itself, e.g. X:'X.

default: [FALSE] - if set to TRUE will cause a (MACSYMA-BREAK) to occur whenever the variables on the SETCHECK list are bound. The break occurs before the binding is done. At this point, SETVAL holds the value to which the variable is about to be set. Hence, one may change this value by resetting SETVAL.

Variable: SETVAL
- holds the value to which a variable is about to be set when a SETCHECKBREAK occurs. Hence, one may change this value by resetting SETVAL. (See SETCHECKBREAK).

Function: TIMER (F)
will put a timer-wrapper on the function F, within the TRACE package, i.e. it will print out the time spent in computing F.

default: [FALSE] - when set to TRUE then the time charged against a function is the time spent dynamically inside the function devalued by the time spent inside other TIMED functions.

Function: TIMER_INFO (F)
will print the information on timing which is stored also as GET('F,'CALLS); GET('F,'RUNTIME); and GET('F,'GCTIME); . This is a TRACE package function.

Function: TRACE (name1, name2, ...)
gives a trace printout whenever the functions mentioned are called. TRACE() prints a list of the functions currently under TRACE. On MC see MACDOC;TRACE USAGE for more information. Also, DEMO("trace.dem"); . To remove tracing, see UNTRACE.

Function: TRACE_OPTIONS (F,option1,option2,...)
gives the function F the options indicated. An option is either a keyword or an expression. The possible Keywords are: Keyword Meaning of return value ---------------------------------------- NOPRINT If TRUE do no printing. BREAK If TRUE give a breakpoint. LISP_PRINT If TRUE use lisp printing. INFO Extra info to print. ERRORCATCH If TRUE errors are caught. A keyword means that the option is in effect. Using a keyword as an expression, e.g. NOPRINT(predicate_function) means to apply the predicate_function (which is user-defined) to some arguments to determine if the option is in effect. The argument list to this predicate_function is always [LEVEL, DIRECTION, FUNCTION, ITEM] where LEVEL is the recursion level for the function. DIRECTION is either ENTER or EXIT. FUNCTION is the name of the function. ITEM is either the argument list or the return value. On MC see DEMO("trace.dem"); for more details.

Function: UNTRACE (name1, ...)
removes tracing invoked by the TRACE function. UNTRACE() removes tracing from all functions.

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