What's the meaning of #0?Confusing efficiency and evaluation when returning pure functions?Split dataset...
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What's the meaning of #0?
Confusing efficiency and evaluation when returning pure functions?Split dataset based on the first columnWhat happens when you divide by ##?Using Through with SlotSequence“Nonatomic expression” error when identifying certain positions in a listTranslating syntax of a pure functionSelect with test function that depends on #Defining an operator: Partially evaluate a Pure FunctionMapping over array/matrix the efficient(compact) wayLooking for a better way use multiple pure functions to condense repetitive code
$begingroup$
Here's a line of code from a handbook written by Stephen Wolfram, which turns out to be very complicated for me.
If[#1 > 2, 2 #0[#1 - #0[#1 - 2]], 1] & /@ Range[50]
The output is:
{1, 1, 2, 4, 4, 2, 4, 4, 8, 4, 4, 8, 16, 4, 2, 16, 4, 2, 4, 4, 8, 4, 4, 8, 16, 4, 8, 16, 16, 8, 4, 16, 32, 4, 4, 32, 64, 4, 2, 64, 4, 2, 4, 4, 8, 4, 4, 8, 16, 4}
I am confused about the Slot 0(#0) here, or how could I break down the code and understand it?
pure-function
asked 2 hours ago
ShawnShawn
182
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$endgroup$
add a comment |
$begingroup$
Here's a line of code from a handbook written by Stephen Wolfram, which turns out to be very complicated for me.
If[#1 > 2, 2 #0[#1 - #0[#1 - 2]], 1] & /@ Range[50]
The output is:
{1, 1, 2, 4, 4, 2, 4, 4, 8, 4, 4, 8, 16, 4, 2, 16, 4, 2, 4, 4, 8, 4, 4, 8, 16, 4, 8, 16, 16, 8, 4, 16, 32, 4, 4, 32, 64, 4, 2, 64, 4, 2, 4, 4, 8, 4, 4, 8, 16, 4}
I am confused about the Slot 0(#0) here, or how could I break down the code and understand it?
pure-function
asked 2 hours ago
ShawnShawn
182
New contributor
Shawn is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
add a comment |
$begingroup$
Here's a line of code from a handbook written by Stephen Wolfram, which turns out to be very complicated for me.
If[#1 > 2, 2 #0[#1 - #0[#1 - 2]], 1] & /@ Range[50]
The output is:
{1, 1, 2, 4, 4, 2, 4, 4, 8, 4, 4, 8, 16, 4, 2, 16, 4, 2, 4, 4, 8, 4, 4, 8, 16, 4, 8, 16, 16, 8, 4, 16, 32, 4, 4, 32, 64, 4, 2, 64, 4, 2, 4, 4, 8, 4, 4, 8, 16, 4}
I am confused about the Slot 0(#0) here, or how could I break down the code and understand it?
pure-function
asked 2 hours ago
ShawnShawn
182
New contributor
Shawn is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
Here's a line of code from a handbook written by Stephen Wolfram, which turns out to be very complicated for me.
If[#1 > 2, 2 #0[#1 - #0[#1 - 2]], 1] & /@ Range[50]
The output is:
{1, 1, 2, 4, 4, 2, 4, 4, 8, 4, 4, 8, 16, 4, 2, 16, 4, 2, 4, 4, 8, 4, 4, 8, 16, 4, 8, 16, 16, 8, 4, 16, 32, 4, 4, 32, 64, 4, 2, 64, 4, 2, 4, 4, 8, 4, 4, 8, 16, 4}
I am confused about the Slot 0(#0) here, or how could I break down the code and understand it?
pure-function
pure-function
asked 2 hours ago
ShawnShawn
182
New contributor
Shawn is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 2 hours ago
ShawnShawn
182
New contributor
Shawn is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 2 hours ago
ShawnShawn
182
New contributor
Shawn is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 2 hours ago
ShawnShawn
182
asked 2 hours ago
ShawnShawn
182
182
New contributor
Shawn is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
Shawn is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
Shawn is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
add a comment |
add a comment |
1 Answer
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$begingroup$
#0 refers to the function itself. This is consistent with the "0th" argument being the head of an expression.
Example:
Print[#0] &[]
(* prints Print[#0]& *)
In practice, this is useful for writing recursive functions. This is what it is used for in your example. The example could be rephrased as
f[x_] := If[x > 2, 2 f[x - f[x - 2]], 1]
answered 2 hours ago
SzabolcsSzabolcs
160k14437934
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1 Answer
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1 Answer
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active
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active
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votes
$begingroup$
#0 refers to the function itself. This is consistent with the "0th" argument being the head of an expression.
Example:
Print[#0] &[]
(* prints Print[#0]& *)
In practice, this is useful for writing recursive functions. This is what it is used for in your example. The example could be rephrased as
f[x_] := If[x > 2, 2 f[x - f[x - 2]], 1]
answered 2 hours ago
SzabolcsSzabolcs
160k14437934
$endgroup$
add a comment |
$begingroup$
#0 refers to the function itself. This is consistent with the "0th" argument being the head of an expression.
Example:
Print[#0] &[]
(* prints Print[#0]& *)
In practice, this is useful for writing recursive functions. This is what it is used for in your example. The example could be rephrased as
f[x_] := If[x > 2, 2 f[x - f[x - 2]], 1]
answered 2 hours ago
SzabolcsSzabolcs
160k14437934
$endgroup$
add a comment |
$begingroup$
#0 refers to the function itself. This is consistent with the "0th" argument being the head of an expression.
Example:
Print[#0] &[]
(* prints Print[#0]& *)
In practice, this is useful for writing recursive functions. This is what it is used for in your example. The example could be rephrased as
f[x_] := If[x > 2, 2 f[x - f[x - 2]], 1]
answered 2 hours ago
SzabolcsSzabolcs
160k14437934
$endgroup$
#0 refers to the function itself. This is consistent with the "0th" argument being the head of an expression.
Example:
Print[#0] &[]
(* prints Print[#0]& *)
In practice, this is useful for writing recursive functions. This is what it is used for in your example. The example could be rephrased as
f[x_] := If[x > 2, 2 f[x - f[x - 2]], 1]
answered 2 hours ago
SzabolcsSzabolcs
160k14437934
answered 2 hours ago
SzabolcsSzabolcs
160k14437934
answered 2 hours ago
SzabolcsSzabolcs
160k14437934
answered 2 hours ago
SzabolcsSzabolcs
160k14437934
160k14437934
add a comment |
add a comment |
Shawn is a new contributor. Be nice, and check out our Code of Conduct.
Shawn is a new contributor. Be nice, and check out our Code of Conduct.
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