Questions tagged [language-design]
for questions about the design of the Mathematica language itself
148 questions
16
votes
3
answers
422
views
Why is the first argument of the SetDelayed evaluated?
In[1]: f=g;
In[2]: SetDelayed[f[x_],x^2];
In[3]: ?f
Global`f
f=g
In[4]: ?g
Global`g
g[x_]:=x^2
However, SetDelayed has the ...
- 397
9
votes
1
answer
510
views
Why is Reap result nested? [closed]
A minimal (toy) example for my question:
i= 1;
Reap[Do[Sow[i = (i + 1)^2], {4}]]
(* {Null, {{4, 25, 676, 458329}}} *)
I presume the entire result is a ...
- 12.1k
12
votes
1
answer
157
views
Which symbol gets DownValues or OwnValues when using SetDelayed?
I have been looking at various usages of Pattern objects. Here's a number of ways to define the same thing:
mod[x_] := {x}
...
- 11.5k
1
vote
0
answers
99
views
What's in a Name? [closed]
StringReplacePart["StringReplacePart","At",{14,17}] ... Surely you can't be serious? ...
Naming Matters: I think what and how we call things is ...
- 6,086
13
votes
1
answer
565
views
What naming conventions are used for functions? [closed]
I thought there were patterns to how functions were named, but after looking carefully it seems I can always find exceptions. For instance
FindThreshold = Action + Object
SetAlphaChannel = Action + ...
- 31.8k
9
votes
1
answer
271
views
Different Set Semantics - Why is assoc["a"] =. different from assoc[["a"]] =.?
Accessing parts of an Association can be done either using Part or the [] extraction ...
- 6,086
6
votes
2
answers
541
views
PlotLegends "Expressions" default for ListPlot?
gwr pointed out an apparent problem with setting a default Option value of PlotLegends for DateListPlot. I traced the problem ...
- 273k
0
votes
2
answers
54
views
How to make Mathematica to assemble components we already have like a regular input
Suppose we have the following list:
{5, 3}
I want to add the -> to the end of the first element in the list in Mathematica ...
- 313
26
votes
1
answer
838
views
What's the point of ContainsAll, ContainsAny and friends?
Mathematica 10.2 contains a few new functions that test set containment: ContainsAll, ContainsAny and a few others. The ...
- 36.4k
4
votes
1
answer
343
views
Why is there a difference when formulating patterns for Select and FirstPosition?
Select[{1, 2, 4, 7, 6, 2}, # > 2 &]
Gives {4, 7, 6}. OK!
So one should think that the following would work:
...
- 239
14
votes
4
answers
414
views
Association's Key[key] extraction different in V10.1/V10.2
V10.1:
<|a -> 1|>[Key @ a]
(* Missing["KeyAbsent", Key[a]]*)
V10.0:
<|a -> 1|>[Key @ a]
(* 1 *)
Bug or ...
- 6,086
8
votes
1
answer
1k
views
Set PlotTheme globally?
Can one set a default PlotTheme globally?
While I recognize one can make lots of workarounds to sort of do this:
Go to ...
- 14.6k
39
votes
2
answers
9k
views
Why do Mathematica list indices start at 1? [closed]
In most programming languages, container indices start at 0. This is not random or hardware-related; for example Dijkstra's article explains why zero-based indices make sense.
What are the reasons ...
- 767
3
votes
3
answers
124
views
Orderless storage of tabulated function values
I would like to elaborate on my previous question Function of arguments given in non-fixed order and a relevant related one Best practice of passing a large number of parameters to functions
I find ...
- 1,420
6
votes
1
answer
315
views
when two associations are equal?
<|a -> 2, b -> 3|> == <|b -> 3, a -> 2|> returns False; can anybody explain why? If I am not mistaken ...
- 1,420
48
votes
3
answers
1k
views
Is FullGraphics an abandoned function? Is there an alternative?
FullGraphics hasn't worked entirely for a long time and the situation appears to be getting worse instead of better. In Mathematica 10.0, 10.1, 11.3, 12.3 up to 13....
- 273k
43
votes
0
answers
1k
views
Performance problems in new Sequence functions
The new-in-10.1 Sequence* family of functions should provide newly optimized methods for handling sequence problems. Happily in some cases they do! For example ...
- 273k
13
votes
2
answers
902
views
Why aren't parentheses ( ) an expression in Mathematica?
Why aren't parentheses ( ) an expression in Mathematica?
Can I get an expression in a form where parentheses are represented by an expression?
- 1,897
13
votes
1
answer
400
views
Is there a good reason for the removal of this FrameTicks syntax?
In past versions of Mathematica one could use a terse syntax for FrameTicks:
{bottom, left, top, right}
In 10.1 this syntax is no longer recognized requiring the ...
- 273k
7
votes
4
answers
557
views
Strange answer from StringReplace
I have a list of strings and I would check if there is an empty string element, that's "", because I need to replace it with a "0". I try the following
...
- 2,047
12
votes
2
answers
299
views
Why are there a lot of input forms in Mathematica?
I'm a novice in using Mathematica.
Please can you explain why there are a lot of input forms in Mathematica such as standard, prefix, postfix and infix?
- 583
3
votes
0
answers
435
views
Mixing Wolfram Language & WolframAlpha Queries - How robust is it?
The advent of Mathematica in the cloud and linguistic input potentially transforms expectations of the Wolfram Language's programming model and its inherent robustness. An example of this comes form ...
- 6,086
7
votes
2
answers
314
views
Built in function without Attributes Listable works as if it has Attributes Listable
Can Built-in function works as if it has Attributes Listable even if it doesn't have that ...
- 20k
13
votes
2
answers
3k
views
Why did Mathematica choose brackets for function arguments over parentheses?
This is a non-technical question. I'm just curious why Mathematica breaks the convention that parentheses are widely used for function arguments. What's the advantage of ...
- 459
13
votes
1
answer
347
views
Why can AppendTo modify a referenced list in-place but Part cannot?
Part, AppendTo, PrependTo, AddTo, etc. allow in-place modification of a list, but only Part requires that the list be referenced through a simple symbol, e.g. the following all does what you'ld expect:...
- 175
8
votes
2
answers
317
views
Why does ToRules return a Sequence?
Why does ToRules return a Sequence expression? Why doesn't it return directly what ...
- 236k
4
votes
0
answers
1k
views
DSolve versus DSolveValue [closed]
I've just discovered the new command DSolveValue in Mathematica 10. Is this new command now the preferred instead of DSolve? Is ...
- 15k
11
votes
3
answers
248
views
Lists for built-in functions that can work without brackets
I just noticed that Exit and Quit can work without brackets i.e. a single
Exit
or
...
- 68.4k
29
votes
1
answer
1k
views
Why some built-in functions are slow
I just wonder why some built-in functions are slower compared to some other ways using more than one built-in functions for doing same job.
consider this example:
...
- 20k
16
votes
8
answers
3k
views
Product of elements of a list
Sum is for functions; Total is for a list. Product is for a function; what is the command ...
user21376
21
votes
1
answer
773
views
Why won't SparseArray let me store values with the head List?
When you attempt to define a SparseArray with elements that have the head List it complains:
...
- 273k
24
votes
2
answers
698
views
Why doesn't a Composition[] hold its arguments and what can be done about it?
Now that Composition (also RightComposition) has shorthand syntax I am more inclined to use it, however what I feel should be ...
- 273k
4
votes
1
answer
206
views
Why even try the semantic constraints, if expression can't match the pattern structure?
This result is unexpected:
Trace[MatchQ[{7}, {_?NumberQ, __}], NumberQ] (* -> {{NumberQ[7], True}} *)
Why evaluate NumberQ...
- 793
6
votes
1
answer
380
views
Why does Mathematica list the variables in a double integral backwards?
I am an advanced novice Mathematica user and have done a fair amount of single-variable calculus things with it. This semester I am using Mathematica for multi-variate calculus and when I tried to ...
- 61
3
votes
1
answer
159
views
Why is left NumberPadding always applied in NumberForm?
I would like to display numbers like 9.0001 and 10.0001 in the fixed-width form of xx.xxxx. ...
- 7,810
120
votes
1
answer
3k
views
Why are numeric division and subtraction not handled better in Mathematica?
There is something that has been troubling me for a while. At least through version 10.0 the performance of a / b and a - b is ...
- 273k
20
votes
2
answers
6k
views
Why does Mathematica order polynomial forms in reverse from traditional order?
I could very well be missing something obvious, but this has always bugged me with Mathematica and I don't know why it does it or how to fix it.
If I enter any polynomial, say, x^2 + x - 1 for ...
- 545
8
votes
1
answer
2k
views
why mathematica outputs "True" sometimes in outputs that are conditional to mean "in all other cases"? [closed]
consider this simple Input:
Probability[g <= m && m <= -g + 1,
{m, g} \[Distributed] UniformDistribution[{{0, 1}, {0, gg}}]]
which generates a ...
45
votes
5
answers
2k
views
Why is there no PositionFunction in Mathematica?
Too often I have seen the programs of inexperienced users greatly slowed by using Position in an iterative fashion, when far faster would have been to compute a ...
- 273k
21
votes
1
answer
448
views
Why are some option values symbols, other strings?
Is there a rationale, beyond historical accident, why some Mathematica option values are strings, while others are symbols?
It seems natural that some value spaces, e.g. named color schemes, are so ...
- 15.2k
3
votes
1
answer
2k
views
Why is Euler's number an uppercase "E" and not a lowercase "e"?
Why is Euler's number an uppercase "E" and not a lowercase "e"?
Isn't Euler's Number normally expressed with a lowercase "e"?
- 1,565
17
votes
1
answer
617
views
Why doesn't Mathematica pack Boolean arrays?
I've been wondering about this for a while now, so I'm going to ask. This is a question about the design of Mathematica, which perhaps cannot be directly answered by anyone but the designers, however ...
- 273k
17
votes
3
answers
2k
views
Specifying string patterns in DeleteCases
It seems that DeleteCases is not compatible with string patterns, at least directly (see, for example, this question). Is this true? If so, why is this the case? ...
- 10.5k
22
votes
3
answers
5k
views
Why does Mathematica use [[ ]] notation for array indexing?
I am confused by why Mathematica uses [[3]] to get the 3rd element, or [[i,j] to get the i,j-th element of a 2D array.
This ...
user1602
21
votes
1
answer
583
views
Are there advantages to using additional arguments of common functions rather than alternative ways of calculating with lists?
(Apologies for the long question title.)
One of the interesting, if sometimes confusing, things about Mathematica is that there is always more than one way to do things. Even intermediate users can ...
- 34.5k
9
votes
1
answer
298
views
DiracDelta attributes
Is there any reason why DiracDelta isn't a NumericFunction but DiracComb is?
I just ate a ...
- 42.8k
88
votes
4
answers
49k
views
Why round to even integers?
According to the Mathematica help:
Round rounds numbers of the form x.5 toward the nearest even integer.
For example:
Round[{0.5, 1.5, 2.5, 3.5, 4.5}]
gives
...
- 14.3k
16
votes
3
answers
5k
views
Why don't * and ^ work as I expected on matrices? [closed]
For example, this input...
{{1, 2}, {3, 4}}*{{1, 2}, {3, 4}}
produces this output...
{{1, 4}, {9, 16}}
and this input...
<...
- 1,017