[r6rs-discuss] [Formal] Simplifying conditions
sperber at informatik.uni-tuebingen.de
Sun Nov 26 06:00:49 EST 2006
AndrevanTonder <andre at het.brown.edu> writes:
> Any simplifications would indeed be nice.
So how does this suggestion look to you?
The condition system distinguishes between simple conditions and
compound conditions. A compound condition consists of an ordered set
of simple conditions. Thus, every condition can be viewed as an
ordered set of simple component conditions: If it is simple, the set
consists of the condition itself; if it is compound, it consists of
the simple conditions that compose it.
The following procedures replace the ones in the current draft:
(make-condition-type id parent field-names) <as before>
(condition-type? thing) <as before>
(make-condition type alist)
Make-condition creates a simple condition value belonging condition
type type. The following arguments must be an association list mapping
field names to arbitrary values. There must be a pair in the
association list for each field of type and its direct and indirect
supertypes. Make-condition returns the condition value, with the
argument values associated with their respective fields.
(condition? thing) <as before>
(condition-has-type? condition condition-type) <as before>
Condition must be a condition. This returns a list of the component
conditions of condition.
(condition-ref condition type field-name)
Condition must be a condition, type a condition type, and field-name a
symbol naming a field of type or its direct or indirect supertypes.
Moreover, condition must be a simple condition of type type, or a
compound condition containing a simple condition of type type.
Condition-ref returns the value of the field named by field-name in
the first component condition of condition that has type type.
(make-compound-condition condition0 condition1 ...)
Make-compound-condition returns a compound condition consisting of the
component conditions of condition0, condition1, in that order.
The following replaces the current specification of the `condition'
(condition <type-field binding> ...)
This creates a condition value. Each <type-field binding> must be of
( <condition type> <field binding> ...)
Each <field binding> must be of the form
( <field name> <exp> )
where <field> is a field identifier from the definition of
The condition returned by condition is created by a call of form
(make-condition <condition-type> '<field-name> <exp>...)
with the condition types retaining their order from the condition
Cheers =8-} Mike
Friede, Völkerverständigung und überhaupt blabla
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