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(guile.info)General option interface

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General option interface
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We will use the expression `<group>' to represent `read', `print',
`debug' or `evaluator'.

Low level
---------

 - primitive: <group>-options-interface
 - primitive: read-options-interface [SOME-INT]
 - primitive: print-options-interface [SOME-INT]
 - primitive: evaluator-traps-interface [SOME-INT]
 - primitive: read-options-interface [SOME-INT]
     [FIXME: I have just taken the comments for C routine scm_options
     that implements all of these.  It needs to be presented better.]

     If scm_options is called without arguments, the current option
     setting is returned.  If the argument is an option setting,
     options are altered and the old setting is returned.  If the
     argument isn't a list, a list of sublists is returned, where each
     sublist contains option name, value and documentation string.

User level
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 - procedure: <group>-options [arg]
 - procedure: read-options [arg]
 - procedure: print-options [arg]
 - procedure: debug-options [arg]
 - procedure: traps [arg]
     These functions list the options in their group.  The optional
     argument ARG is a symbol which modifies the form in which the
     options are presented.

     With no arguments, `<group>-options' returns the values of the
     options in that particular group.  If ARG is `'help', a
     description of each option is given.  If ARG is `'full',
     programmers' options are also shown.

     ARG can also be a list representing the state of all options.  In
     this case, the list contains single symbols (for enabled boolean
     options) and symbols followed by values.
[FIXME: I don't think 'full is ever any different from 'help.  What's
up?]

 - procedure: <group>-enable option-symbol
 - procedure: read-enable option-symbol
 - procedure: print-enable option-symbol
 - procedure: debug-enable option-symbol
 - procedure: trap-enable option-symbol
     These functions set the specified OPTION-SYMBOL in their options
     group.  They only work if the option is boolean, and throw an error
     otherwise.

 - procedure: <group>-disable option-symbol
 - procedure: read-disable option-symbol
 - procedure: print-disable option-symbol
 - procedure: debug-disable option-symbol
 - procedure: trap-disable option-symbol
     These functions turn off the specified OPTION-SYMBOL in their
     options group.  They only work if the option is boolean, and throw
     an error otherwise.

 - syntax: <group>-set! option-symbol value
 - syntax: read-set! option-symbol value
 - syntax: print-set! option-symbol value
 - syntax: debug-set! option-symbol value
 - syntax: trap-set! option-symbol value
     These functions set a non-boolean OPTION-SYMBOL to the specified
     VALUE.