Questions tagged [argument-patterns]
Questions concerning argument patterns used as formal arguments in function definitions (e.g., := expressions) to restrict the kinds of values that can be passed as actual arguments. Also questions about how such patterns can be used to achieve function overloading.
155
questions
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114
views
How to make a pattern that matches only when one of the argument's Head is a Plus?
I am trying to set up rules as follows:
ClearAll[CircleTimes];
If the arguments are the same the output is zero:
...
- 8,075
5
votes
2
answers
299
views
Map a two argument function to every element on list
I'm new to use the amazing map function in Mathematica, and I've found it really elegant to program in simple lines of code. However, I'd like to perform more elegant stuff. I've found this question, ...
- 497
0
votes
1
answer
43
views
How to define a mixed pattern consisting of string and regular patterns for function definition (using SetDelayed)?
I'm kinda stuck here, and I could really use some help:
I want to define a function, let's call it quarterValue, that accepts a ...
- 122
1
vote
1
answer
51
views
Why this pattern can't be matched? [closed]
My code is {x,y,z}/.PatternSequence[x,y]->t.I think the answer is {t,z},while the output is still ...
- 71
3
votes
1
answer
213
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Pattern matching with two variables - derivatives on 4-vectors
I am interested in pattern matching with two variables and not just one, and more specifically implementing derivatives on 4-vectors. In the case of interest the 4-vectors have two indices; one is in ...
- 4,113
0
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0
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38
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How to specify specific (custom) function arguments
Suppose that I want to have a function that is evaluated only when a user-specific, predefined flag is given out of a list of possible flags. For example
...
- 743
1
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0
answers
73
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How to test for arguments for a pattern that is of a positive Integer OR Infinity so that both filter through to the definition on RHS?
How can I filter an argument of a function so that definition works on positive Integers (y >= 0) or Infinity? It will ...
- 1,647
2
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0
answers
54
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How to specify complicated patterns in function arguments?
Unfortunately, I have not found in documentation how to create complicated patterns in arguments of a function
Consider a toy example. Say, I would like to have a simple function
...
- 654
0
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0
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47
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Detecting whether a function is initially defined with the form R[x,y] or R[x_,y_], etc
I have a very long code that may have errors in definition of functions and I want to trace these errors.
Is there any attribute or function to detect whether a function is initially defined in the ...
- 340
0
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1
answer
100
views
Matching a Dynamic Argument Pattern
times is a list of times i.e. matching {{hour_, min_, sec_Real}..}.
I want to call ...
- 750
2
votes
1
answer
73
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Defining function with arguments in a specific pattern similar to Graphics[]
I'm trying to define a function that is of this form:
...
- 107
1
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1
answer
64
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Denoting the whole in Position/Extract/ReplacePart
Position returns lists of numbers consumed by Extract, ReplacePart and others as "...
7
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203
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How to set deeper patterns in arguments within function definitions. For example if an argument must be a list of 1 or more strings
Suppose I want to define a function whose argument must be a List of only Strings and List must have at least one member. I know how to require that the Head must be a List but how does one qualify ...
- 1,647
4
votes
0
answers
111
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Lint checker for overlapping or conflicting function signature patterns
In building a system like Mathics (or anything having the number of builtin functions of Mathematica) there are lots of function definitions. I would like to sanity check or lint check the pattern in ...
- 221
4
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0
answers
56
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Preventing $-renaming of pattern names in lexically-scoped constructs
When you use a lexically-scoped construct like With or Function to perform replacements in an expression, Mathematica might ...
- 7,739
7
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0
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68
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Why does Longest not work on OptionsPattern?
When having a function with optional arguments and options, I frequently find myself writing something like this:
...
- 23.2k
8
votes
2
answers
289
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How to check the number of function arguments given by the user
Suppose I have defined the following function inside a package that can take 2 arguments.
f[x_,y_]:={x,y}
So, if the user gives ...
- 1,018
0
votes
1
answer
65
views
Restrict the domain of a function (and plot) it) when it depends on the value of a parameter
I know similar questions have been asked, but I am very new at Mathematica and other questions/answers are quite complex and do not suit the code I want to write.
I want to restrict the domain of the ...
- 107
2
votes
1
answer
24
views
Refer to argument in condition for other argument
The condition for b here doesn't recognize a. How can I fix this?
...
- 1,055
0
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0
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92
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How to convert Symbol to Number?
Question
I have a variable x which is associated with the number 1 : x= 1
In the program, I faced with the data type problem ...
- 113
1
vote
2
answers
93
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Unusual performance of the Cases function [closed]
Recently I was surprised by unusual performance of Cases function. The code
...
- 654
2
votes
0
answers
74
views
How does Mathematica choose which function definition to use?
I was wondering what the process of matching function arguments arguments against different function definitions actually looks like for Mathematica.
(Just to be clear, I'm not simply looking for an ...
- 7,739
7
votes
0
answers
117
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Exceeding recursion limit with no obvious recursion: Optional pattern-matching causing nonlocal behavior
So, I've come across something strange, and wanted to get a deeper understanding of what was going on. Consider the following code:
...
- 7,739
2
votes
1
answer
103
views
Function of function with arbitrary number of arguments
Given the function (simplified example)
g[En_, k1_] := En^2 *k1
I have to plug it inside another expression, where En is ...
- 350
0
votes
1
answer
75
views
Using conditions to construct a function [closed]
This is the hint my professor provided.
We have 6 separate cases to define the function pow[x_ , r_].
The first case is where ...
- 51
4
votes
1
answer
94
views
Force results to be displayed in a way often seen in traditional math [closed]
I want to get my output in the form that I would write by hand. I have tried with TraditionalForm, but it did not work.
I've looked at several answers in this SE ...
- 309
6
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0
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112
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Difference between the infinite rewriting behavior of evaluation and ReplaceRepeated
In the documentation tutorial/Evaluation it's said that:
Every time the expression changes, the Wolfram Language effectively starts the evaluation sequence over ...
- 553
0
votes
1
answer
75
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passing splice instructions
Consider some passing splice instructions using start,stop,step pattern
...
- 902
1
vote
3
answers
77
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My rule does not do anything (understandably)
I want a rule that would transform, for example, And[i,F[j,k],l,G[m,F[j,k],n],p] into And[i,F[j,k],l,G[m,T,n],p], where ...
- 2,037
0
votes
0
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18
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How to memoize with patterns? [duplicate]
Here is an artificial example to explain what I am up to. Define
ClearAll[f]
f[x_, y_] := f[x, y] = If[x == 0, g[y], g[f[x - 1, y]]]
Then ...
- 2,037
0
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0
answers
52
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Head of complex sum
We have:
1 + 2 I + 3 + 4 I // Head
Complex
and
1 + 2 I + 3/5 + 4/5 I // Head
Complex
But we get:
...
- 11.3k
1
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0
answers
62
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How conflicting patterns are resolved?
I often find myself doing something like this (probably poor example, sorry)
f[x_] := 0
f[x_Plus] := 1
In the back of my mind generally ...
- 515
5
votes
1
answer
81
views
How to define a parameter with both Optional and PatternTest
Why this doesn't work?
k[x_Integer:2?(#>0&)]:=x^2
k[] (*should be 4*)
k[2] (*should be 4*)
These following are all working as expected:
...
- 3,644
1
vote
2
answers
51
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How to define a function that acts invidually on a varible number of arguments
I am trying to generate a function that applies to each argument for any number and type of arguments. The function might work like this:
...
- 1,647
2
votes
1
answer
79
views
Write repeated expressions within a rule more simply
Is it possible to shorten the length of a (delayed) rule (i.e. lhs :> rhs) when there are expressions which repeat several times? Those expressions involve ...
- 483
1
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0
answers
33
views
Is there a way to get the calling information inside the body of a function defined using down value?
Suppose a function has multiple argument structure like follows:
...
- 8,075
3
votes
1
answer
376
views
How to use patterns to specify variable type as Boolean (True, False) in analogy to x_Integer, x_Real, x_Complex, x_List, etc
Say I define a function f[x_, y_]:= ..., the concrete definition of which is not important now.
What is important though is, that I want ...
- 621
3
votes
2
answers
72
views
Setting nested optional argument with a default when unpacking from a given Head
I have a head that holds a single argument, and I want to unpack the value inside it while also assigning a symbol to the value itself, for example:
...
- 257
1
vote
1
answer
39
views
FilterRules works in DateListPlot but not in Plot
I just experience the following problem (this is a MWE just to illustrate). First DateListPlot
...
- 5,453
2
votes
1
answer
104
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Prevent an expression from evaluating a certain way (pattern-matching?)
I've been trying to write some simple code to let me use physics vector notation: $\hat{x}$, $\hat{y}$, $\hat{r}$, and $\hat{\theta}$.
...
- 529
2
votes
1
answer
76
views
How can I make a function that expects a list of variables behave like a multivariate function? [closed]
I am trying to convert a user defined function that takes two or more variables into a user defined function that takes a list of variables. However, it seems Mathematica treats variables and ...
- 143
0
votes
1
answer
87
views
How do I define a function that accepts a subscripted variable?
How do I define a function with subscripted variable? I want to write the following expression
$\qquad f[a_9] =1+ a_7 + a_9$
I wrote
...
- 101
22
votes
7
answers
824
views
How to replace all elements of a list by a rule "element" -> "element_"
I have a list:
{a, b, c, d, e, f, g, h, i, j}
The goal is to get:
{a_, b_, c_, d_, e_, f_, g_, h_, i_, j_}
I can replace ...
- 687
6
votes
2
answers
216
views
How to divide list according to the pattern?
There is a list of lists:
{{0,0,0}, {0,0,1}, {0,1,0}, {0,1,1}, {1,0,0}, {1,0,1}, {1,1,0}, {1,1,1}}
I need to regrup it's elements according to a pattern: "if the ...
- 687
0
votes
0
answers
62
views
Delayed Rule right-hand-side mis-evaluation
Outline
I am trying to create a rule that will give me a minus sign if the number of times A is applied on X is odd where A is some οperator and X a random quantity.
Some of the configurations of ...
- 65
1
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1
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300
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Define Function explicitely with List as argument [duplicate]
Background
There are multiple ways to define Functions. I would assume all methods are equivalent, and allow for the same options. However, I fail to find the ...
- 1,535
1
vote
1
answer
164
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n derivatives on a function of n variables
I want to derive an expression with respect to each variable of a function $f: \mathbb R^n \rightarrow \mathbb R$. More precisely:
$\left(\prod_{i=1}^n\frac{\partial}{\partial_{x_i}}\right) g(f(x_1,...
- 73
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1
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83
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How to have NonlinearModelFit not evaluate a function too early?
This is a follow up of my previous question How can I define the following function for arbitray values of the arguments? that received no attention so here I will try to be more concise with the ...
- 513
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3
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299
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How can I check if a function can be written as $a * \sin (b * x + c) + d$?
I want to write a function that takes another function, say $f(x)$ and a variable $x$ as input and return True it this function can be written in the form ...
0
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1
answer
110
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How can I define the following function for arbitray values of the arguments?
Consider the following function
a[m_, l_] = 1/Log[m/l];
with this function I define
...
- 513