From: Emerson <emerson@harvestman.net>

Date: Tue, 16 Sep 2003 01:09:46 +0100

To: <public-qt-comments@w3.org>

Message-ID: <000001c37be6$d7009520$ec3e353e@genesis>

Date: Tue, 16 Sep 2003 01:09:46 +0100

To: <public-qt-comments@w3.org>

Message-ID: <000001c37be6$d7009520$ec3e353e@genesis>

Rather than raising a type error during evaluation of StepExpr, which as far as I can see is simply a way of handling the case where an expression does not return a sequence of nodes, I propose an alternative. Let us first take, E1 & E2 to be two StepExpr's, and T1 & T2 to be the return types of E1 & E2 respectively. Assume E1 to be a valid axis step returning a sequence of nodes. Given the following XPath E1/E2 If E2 evaluates to a numeric result then the expression should be evaluated as; E1/child::*[T2] Such that E2 is substituted with an expression returning the T2'th child of E1. If E2 evaluates to a literal result then the expression should be evaluated as; E1/child::T2 Such that E2 is substituted with an expression returning all children which match the node test given by the string literal T2. If E2 Evaluates to a boolean result then the expression should be evaluated as; E1/* If and only if the boolean result evaluates to true, otherwise the expression should be evaluated as; E1 Variable references would be handled as the appropriate primitive type above. Since there is already a special rule for numbers in predicate expressions, this is only a logical extension plus or minus a little translation. Some of these recommendations are already used in the Xpointer specification (a derivative of Xpath 1.0) Surely doing something wise (and potentially very useful) with a return type is better than giving a type error. After all, its not like the type error is any more graceful than saying "boom!" your expression did not evaluate. Can anyone show an example of how the functionality given above can be provided in a single line Xpath statement (i.e. without the use of branching statements such as "if") without the extensions that I have proposed here ? emersonReceived on Monday, 15 September 2003 20:13:36 UTC

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