# mfenced element is not equivalent to its expanded form #478

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opened this issue May 22, 2013 · 3 comments

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### fred-wang commented May 22, 2013

 Per the MathML spec http://www.w3.org/TR/MathML3/chapter3.html#presm.mfenced $x y$  should be equivalent to $x y$  but that's not the case (spacing, strechiness). This is the cause of regression #475. (in general inconsistency between mfenced and the mrow equivalent construction in all MathML implementations is one reason that motivates deprecating mfenced and working only on mrow+mo)
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### dpvc commented May 22, 2013

 The HTML-CSS and SVG renderers do use  elements internally to do the rendering of the fences and separators, but you are right, they do force stretchy=true and force the tex-class to be open and close rather than letting the dictionary decide, which is where the stretchy and spacing differences come from. This would not be hard to fix, and I agree that it should be done in the next release. Now that the TeX input doesn't use  directly, that will be easier to do (TeX used to map \left...\right directly to , which is why they were forced to be stretchy and spaced properly for that).

### dpvc pushed a commit to dpvc/MathJax that referenced this issue Feb 11, 2014

 Make mfenced match mrow+mo form, and make U+2223 and U+2225 stretchy … 
…in pre- and postfix positions (to match Firefox). Resolves issue mathjax#478.
 641d669 

### dpvc pushed a commit to dpvc/MathJax that referenced this issue Feb 12, 2014

 Merge branch 'issue478' into develop. Issue mathjax#478. 
 126bd1c 

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### dpvc commented Feb 12, 2014

 => Merged.

### dpvc pushed a commit to mathjax/MathJax-test that referenced this issue Apr 21, 2014

 Add test for issue mathjax/MathJax#478. 
 1dac292 
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### dpvc commented Apr 21, 2014

 => In Test Suite. MathMLToDisplay/Presentation/GeneralLayout/mfenced/issue478.html