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Frequently Asked Questions

WReach? Is that connected to WRI somehow?

The "WR" in my name has nothing to do with the company that develops Mathematica. It is just a coincidence.

Why do you start all your global variable names with $?

I use dollar signs for ad hoc global variables because I have been bitten too many times by accidentally assigning an own-value to a symbol that I happen to use, for example, in a symbolic equation. So I am in the habit of writing $x instead of x. I stick to that convention even for longer symbols like $initialUrl. Just like the regular symbol convention, Mathematica's predefined global symbols all start with a capital letter after the $. My ad hoc symbols always start with a lower case letter, so there is no conflict.

Why do you put semicolons and commas at the beginning of the line instead of at the end like a normal person?

I don't think of it that way. Rather, I switch from horizontal to vertical layout when a single expression is too long to fit on one line. This has the interesting side-effect of making the important delimiters stand out and line up. I first ran into this practice in the SQL community. SQL "programs" have the unpleasant property that they must be written as a single statement -- even if that statement is a hundred lines long (or more!). Sometimes Mathematica expressions share that property.


1d
awarded  Enlightened
1d
awarded  Nice Answer
2d
comment Why can I not replace a Dataset using a rule?
@Szabolcs Good catch. Fixed.
2d
revised Why can I not replace a Dataset using a rule?
changed `Replace` to `ReplaceAll`
2d
answered Why can I not replace a Dataset using a rule?
2d
answered Using Throw within ParallelDo
2d
answered subtleties about variable shadowing in Block[]
Mar
18
comment Time Zone Conversion
I enjoy your clever titles, but might I suggest that you include some indication of the subject matter, perhaps something like Time Zone Conversion: A Theory of Non-Relativity?
Mar
18
answered Time Zone Conversion
Mar
13
answered Dynamic ViewPoint on notebook startup
Mar
11
answered How does Grid operate on Dataset?
Mar
10
awarded  Good Answer
Mar
10
awarded  pattern-matching
Mar
9
revised Can a pattern examine all partitions of a sequence?
edited body
Mar
9
answered Can a pattern examine all partitions of a sequence?
Mar
4
comment Fill Dataset value with result of queries on other Datasets
@alancalvitti I am using 10.0.2. In my first alternative I get an invalid result (with Missing elements) if I use KeySort. The query plans are different, reflecting the fact that KeySort is ascending and KeySortBy is descending. In my second alternative, it does not matter whether the operator is ascending or descending, so I just use the shorter-named ascending KeySort.
Mar
4
answered Fill Dataset value with result of queries on other Datasets
Feb
28
revised Adding Trace produces error messages
added 4 characters in body
Feb
28
answered Adding Trace produces error messages
Feb
24
awarded  Good Answer