CAD11 — interface Parameter

The interface Parameter provides four functions · string get_expression() raises (CadUtility::CadError); · void set_expression(in string e_value) raises (CadUtility::CadError); // operations to allow an expression that may drive geometry

· CadUtility::EntityAttrib get_value() raises (CadUtility::CadError); · void set_value (in CadUtility::EntityAttrib value) raises (CadUtility::CadError); // operations providing access to parameter value Actually “Parameter” is an easy interface. But since we have seen different implementation approaches and since it was not clear for us in every case too what should be handed over to the set-methods and what could be retrieved by the get-methods I write down our assumptions and hope that it will be corrected if that was not the approach you have had in mind: A parameter covers expressions like “a=6” or “a=b+c”, where “a” is the “name” of the expression. getValue() therefore will return the recursive computed value in the case of “b+c” or an error when there is a problem with the computation. In case of “6” getValue() will just return the value “6”. setValue() allows to set a value if the value of “is_read_only” has the value “false”. The type of the handed over value must match the type of CadUtility::EntityAttrib stored by parameter. In the case of “a=6” “is_independent” keeps the value true. In the case “a=b+c” “is_independent” turns to the value “false”. It is a question whether handing over a value like “8” should be allowed at all when the parameter carries an non numeric expression. getExpression() is similar to getValue() with the difference that the return type is a string. setExpression() allows to set expressions like “d+e” or “8”. The values of “is_independent” and “is_read_only” have to be set accordingly. Expression like “a=d+e” and “a=8” should be possible but internally the expression is parsed and “a=” is ignored. Expression like “b=d+k” should be forbidden because they provide a back door to define completely new parameter when name is set to “b”. If this also has been intended this should be made clear. But I guess this would require extra methods that allow to define parameter. Summing up it is actually no problem to omit the value-methods The “expression”-methods can take over the task to handle values because these also can be represented by expressions like “8”.

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