I'm going through the w3cschools XSLT tutorial, and I am at this page: xsl-if.
On that page (in red) is the text <xsl:if test="price > 10">. This works. I modified the code to use "<" and that works fine too.
I tested <xsl:if test="price > 10"> (note the use of > instead of the >). This works too.
But this fails: <xsl:if test="price < 10">. Error is XML Parsing Error: not well-formed and it points to the < symbol in the expression.
If the > symbol worked fine, why did using the < fail? (I'm using FireFox)
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78answers:
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A:
If the > symbol worked fine, why did using the < fail? (I'm using FireFox)
Because the "<" character is one of the few that are illegal within an attribute value (it is the start-of tag character).
From the XML Specification
[10] AttValue ::= '"' ([^<&"] | Reference)* '"'
As can be clearly seen, the "<" and "&" characters are not allowed in any attribute value.
Update: As noticed by @Tomalak, the above should read:
As can be clearly seen, the "<" and "&" characters (unless the latter is part of an entity reference or character reference) are not allowed in any attribute value.
Dimitre Novatchev
2010-08-19 22:01:21
Tomalak
2010-08-19 22:08:10
@Tomalak: Thanks, I updated the answer.
Dimitre Novatchev
2010-08-19 22:12:03
Alejandro
2010-08-19 22:34:39
Tomalak
2010-08-19 23:18:29
Alejandro
2010-08-19 23:40:06
Dimitre Novatchev
2010-08-20 16:45:35
+2
A:
The unencoded "opening" bracket < is generally invalid in XML attribute values as per the XML spec.
While the "closing" bracket > is allowed, using it is actually bad style (IMHO). XML attribute values have to be XML-encoded, period.
Tomalak
2010-08-19 22:02:02
@Tomalak: Why, using '>" instead of `'>'` makes the code so more readable. I even usually reverse `x < y` to `not(x > y -1)`
Dimitre Novatchev
2010-08-19 22:39:03
@Dimitre: That's why I wrote "IMHO". I am quite strict when it comes to value encoding, and I consciously avoid shortcuts and loopholes even if they are documented. `x < y` disturbs my flow of reading not at all. However, seeing `not(x > y -1)` would make me stop and think - even if just for a second. Why should I want that? For me, the increased readability does not outweigh the time I need to think about the expression. For me, it's not economic.
Tomalak
2010-08-19 23:09:52
I think that the reverse of `x < y` it should be `y > x`. And is more readable and more economic. Plus, I never understand why `<` could break the parser and `>` don't! Ja!
Alejandro
2010-08-20 01:04:20
@Dimitre Novatchev: No, you're wrong. Let `x` and `y` both be 2. `2 < 2` is false. But `2 >= 2` is true, so the expressions are not equivalent. @Alejandro is correct.
Eric
2010-08-24 09:58:48
@Eric: By "reverse" I mean the logical negation: `not(x < y)` is equivalent to `y >= x`
Dimitre Novatchev
2010-08-24 12:29:11
+3
A:
You can also see the answer to this on w3schools:
http://www.w3schools.com/xmL/xml_syntax.asp
Entity References
Some characters have a special meaning in XML.
If you place a character like "<" inside an XML element, it will generate an error because the parser interprets it as the start of a new element.