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(guile.info)Examples of option use

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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	*Flyweight representation of the stack at traps.
     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>