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I encounter the following quirk in the Notation package:

consider the following ==> and <== declarations

Notation[
 ParsedBoxWrapper[RowBox["\[DoubleStruckOne]"]]  
  \[DoubleLongRightArrow]
 ParsedBoxWrapper[RowBox[{"Blade", "[", RowBox[{"{", "}"}], "]"}]]
]

and

Notation[
 ParsedBoxWrapper[RowBox[{"\[DoubleStruckOne]"}]]
  \[DoubleLongLeftArrow]
 ParsedBoxWrapper[RowBox[{"Blade", "[", RowBox[{"{", "}"}], "]"}]]
]

the only difference is the Braces in the left hand side RowBox.

It only works this way. If I use either line with a two-way arrow <==>, it will fail in one direction or the other.

Why is that?

Do I have to use another Wrapper/Box?

share|improve this question
    
BTW, I found a (completely unrelated) Typo in the package in lines 440 vs. 446. Nothing serious, but it still lowers my confidence in the package. Not even those guys use an editor/tool that will point out an undefined symbol!? –  NoEscape Oct 2 '12 at 13:35
3  
It is a typo out of nearly 4000 lines; I've written worse. More to the point, undefined symbols are a tricky notion in Mathematica. On line 440, the one symbol is defined, but on 446, the typo now exists as a separate symbol as far as mma is concerned. So, what is there for the editor to pick up on, as this might have been intentional? This is a general problem with languages that have loose methods for defining variables. BTW, I did pull it up in WorkBench (Eclipse): it wasn't highlighted. –  rcollyer Oct 2 '12 at 13:55
    
my calculation is different from just dividing 1/4000. If it takes an unexperienced user 2min to find one typo in a package, what's the expectation value that it is the only one. Almost 0. –  NoEscape Oct 2 '12 at 14:10
4  
On some level that is reasonable, however after you have spent any length of time with a project you stop seeing the flaws. It happens with any form of writing, and the proof readers can suffer from the same tunnel vision. Also, with code of that size and complexity, bugs are guaranteed. Just a fact of life. –  rcollyer Oct 2 '12 at 14:19

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