5.18.3.8 Examples of option use

Here is an example of a session in which some read and debug option handling procedures are used. In this example, the user

1. Notices that the symbols abc and aBc are not the same
2. Examines the read-options, and sees that case-insensitive is set to “no”.
3. Enables case-insensitive
4. Verifies that now aBc and abc are the same
5. Disables case-insensitive and enables debugging backtrace
6. Reproduces the error of displaying aBc with backtracing enabled [FIXME: this last example is lame because there is no depth in the backtrace. Need to give a better example, possibly putting debugging option examples in a separate session.]

     guile> (define abc "hello")
     guile> abc
     "hello"
     guile> aBc
     ERROR: In expression aBc:
     ERROR: Unbound variable: aBc
     ABORT: (misc-error)
     
     Type "(backtrace)" to get more information.
     guile> (read-options 'help)
     keywords	#f	Style of keyword recognition: #f or 'prefix
     case-insensitive	no	Convert symbols to lower case.
     positions	yes	Record positions of source code expressions.
     copy		no	Copy source code expressions.
     guile> (debug-options 'help)
     stack		20000	Stack size limit (0 = no check).
     debug		yes	Use the debugging evaluator.
     backtrace	no	Show backtrace on error.
     depth		20	Maximal length of printed backtrace.
     maxdepth	1000	Maximal number of stored backtrace frames.
     frames		3	Maximum number of tail-recursive frames in backtrace.
     indent		10	Maximal indentation in backtrace.
     backwards	no	Display backtrace in anti-chronological order.
     procnames	yes	Record procedure names at definition.
     trace		no	*Trace mode.
     breakpoints	no	*Check for breakpoints.
     cheap		yes	*This option is now obsolete.  Setting it has no effect.
     guile> (read-enable 'case-insensitive)
     (keywords #f case-insensitive positions)
     guile> aBc
     "hello"
     guile> (read-disable 'case-insensitive)
     (keywords #f positions)
     guile> (debug-enable 'backtrace)
     (stack 20000 debug backtrace depth 20 maxdepth 1000 frames 3 indent 10 procnames cheap)
     guile> aBc
     
     Backtrace:
     0* aBc
     
     ERROR: In expression aBc:
     ERROR: Unbound variable: aBc
     ABORT: (misc-error)
     guile>