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Best practice with Return in Module or Block

What are the use cases for different scoping constructs?Return struct from function (with DownValues)Syntax highlighter shows error for Manipulate when it's inside a Block or a ModuleImplementing local variables of a recursive function with either Module or BlockWhat is the difference between defining a function and specifying the type of argument, versus applying a test to that argument?Is anonymous pure function a scoping construct?How to prevent name clash between arguments of different functions?Difference between variables and functionsfunction fails to use local variable when it is called inside a ModuleModule - Symbols out of scope of lexical scopingScoping construct for dependent constants

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2

$begingroup$

I am a bit confused on the use of Return in either Block or Module when defining a custom function that is used a lot. For instance, The two simple functions (not using initialisation to examplify)

f1[x_] := Module[y,y=x+1; Return[y];];
f2[x_] := Module[y,y=x+1; y];

I am familiar with the differences between Module and Block---see e.g. here---but I don't really understand what the difference between f1 and f2 are in the present case. As someone familiar with other languages, the first seems more natural than the second, especially with respect to the absence of a final semi-colon in the module.

I have noticed that with Return I get a bunch of variables y$1, y$2, ... that get out of scope and not in the other case, but I haven't used it enough to see if it happens also in that case.

Is there a fundamental difference between those two functions, and what is considered best practice?

functions scoping return-value

share|improve this question

edited 7 hours ago

Bulkilol

asked 8 hours ago

BulkilolBulkilol

13344 bronze badges

$endgroup$

• 
  
  
  

  
  6
  

  
  
  
  
  
  

  
  $begingroup$
  Best practice is the 2nd (no Return). Return is a bit foreign to how Mathematica works, and also redundant here. There is absolutely no reason to add it (it doesn't improve readability for someone comfortable with Mathematica—quite the opposite). Note that Return returns from the function, not from the Module. If you had something wrapping the Module, the behaviour would be different.
  $endgroup$
  – Szabolcs
  8 hours ago
  

  
  
  
  

add a comment | 

2

$begingroup$

I am a bit confused on the use of Return in either Block or Module when defining a custom function that is used a lot. For instance, The two simple functions (not using initialisation to examplify)

f1[x_] := Module[y,y=x+1; Return[y];];
f2[x_] := Module[y,y=x+1; y];

I am familiar with the differences between Module and Block---see e.g. here---but I don't really understand what the difference between f1 and f2 are in the present case. As someone familiar with other languages, the first seems more natural than the second, especially with respect to the absence of a final semi-colon in the module.

I have noticed that with Return I get a bunch of variables y$1, y$2, ... that get out of scope and not in the other case, but I haven't used it enough to see if it happens also in that case.

Is there a fundamental difference between those two functions, and what is considered best practice?

functions scoping return-value

share|improve this question

edited 7 hours ago

Bulkilol

asked 8 hours ago

BulkilolBulkilol

13344 bronze badges

$endgroup$

• 
  
  
  

  
  6
  

  
  
  
  
  
  

  
  $begingroup$
  Best practice is the 2nd (no Return). Return is a bit foreign to how Mathematica works, and also redundant here. There is absolutely no reason to add it (it doesn't improve readability for someone comfortable with Mathematica—quite the opposite). Note that Return returns from the function, not from the Module. If you had something wrapping the Module, the behaviour would be different.
  $endgroup$
  – Szabolcs
  8 hours ago
  

  
  
  
  

add a comment | 

$begingroup$

I am a bit confused on the use of Return in either Block or Module when defining a custom function that is used a lot. For instance, The two simple functions (not using initialisation to examplify)

f1[x_] := Module[y,y=x+1; Return[y];];
f2[x_] := Module[y,y=x+1; y];

I am familiar with the differences between Module and Block---see e.g. here---but I don't really understand what the difference between f1 and f2 are in the present case. As someone familiar with other languages, the first seems more natural than the second, especially with respect to the absence of a final semi-colon in the module.

I have noticed that with Return I get a bunch of variables y$1, y$2, ... that get out of scope and not in the other case, but I haven't used it enough to see if it happens also in that case.

Is there a fundamental difference between those two functions, and what is considered best practice?

functions scoping return-value

share|improve this question

edited 7 hours ago

Bulkilol

asked 8 hours ago

BulkilolBulkilol

13344 bronze badges

$endgroup$

f1[x_] := Module[y,y=x+1; Return[y];];
f2[x_] := Module[y,y=x+1; y];

share|improve this question

edited 7 hours ago

Bulkilol

asked 8 hours ago

BulkilolBulkilol

13344 bronze badges

share|improve this question

edited 7 hours ago

Bulkilol

asked 8 hours ago

BulkilolBulkilol

13344 bronze badges

asked 8 hours ago

BulkilolBulkilol

13344 bronze badges

asked 8 hours ago

BulkilolBulkilol

13344 bronze badges

1 Answer
1

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2

$begingroup$

The use case for Return is not to return a value at the end of a scoping construct like Module or Block, but to return something from the middle of the construct:

func[x_] := Module[
 answer1,answer2,
 <code>
 If[isValid[answer1],
 Return[answer1, Module]
 ];
 <more code>
 answer2
]

Here I check a whether some condition is satisfied, and if so I exit the Module early. This could be achieved with a Catch and Throw, but I tend to reserve that more for errors and exceptions. Here I view the Return as a normal operation, and not exceptional.

The caveat here is that the 2-argument form of Return, where the second argument says what to return from, is not documented.

share|improve this answer

answered 4 hours ago

Jason B.Jason B.

50.5k33 gold badges9494 silver badges201201 bronze badges

$endgroup$

add a comment | 

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2

$begingroup$

The use case for Return is not to return a value at the end of a scoping construct like Module or Block, but to return something from the middle of the construct:

func[x_] := Module[
 answer1,answer2,
 <code>
 If[isValid[answer1],
 Return[answer1, Module]
 ];
 <more code>
 answer2
]

Here I check a whether some condition is satisfied, and if so I exit the Module early. This could be achieved with a Catch and Throw, but I tend to reserve that more for errors and exceptions. Here I view the Return as a normal operation, and not exceptional.

The caveat here is that the 2-argument form of Return, where the second argument says what to return from, is not documented.

share|improve this answer

answered 4 hours ago

Jason B.Jason B.

50.5k33 gold badges9494 silver badges201201 bronze badges

$endgroup$

add a comment | 

2

$begingroup$

The use case for Return is not to return a value at the end of a scoping construct like Module or Block, but to return something from the middle of the construct:

func[x_] := Module[
 answer1,answer2,
 <code>
 If[isValid[answer1],
 Return[answer1, Module]
 ];
 <more code>
 answer2
]

Here I check a whether some condition is satisfied, and if so I exit the Module early. This could be achieved with a Catch and Throw, but I tend to reserve that more for errors and exceptions. Here I view the Return as a normal operation, and not exceptional.

The caveat here is that the 2-argument form of Return, where the second argument says what to return from, is not documented.

share|improve this answer

answered 4 hours ago

Jason B.Jason B.

50.5k33 gold badges9494 silver badges201201 bronze badges

$endgroup$

add a comment | 

$begingroup$

The use case for Return is not to return a value at the end of a scoping construct like Module or Block, but to return something from the middle of the construct:

func[x_] := Module[
 answer1,answer2,
 <code>
 If[isValid[answer1],
 Return[answer1, Module]
 ];
 <more code>
 answer2
]

Here I check a whether some condition is satisfied, and if so I exit the Module early. This could be achieved with a Catch and Throw, but I tend to reserve that more for errors and exceptions. Here I view the Return as a normal operation, and not exceptional.

The caveat here is that the 2-argument form of Return, where the second argument says what to return from, is not documented.

share|improve this answer

answered 4 hours ago

Jason B.Jason B.

50.5k33 gold badges9494 silver badges201201 bronze badges

$endgroup$

func[x_] := Module[
 answer1,answer2,
 <code>
 If[isValid[answer1],
 Return[answer1, Module]
 ];
 <more code>
 answer2
]

share|improve this answer

answered 4 hours ago

Jason B.Jason B.

50.5k33 gold badges9494 silver badges201201 bronze badges

answered 4 hours ago

Jason B.Jason B.

50.5k33 gold badges9494 silver badges201201 bronze badges

answered 4 hours ago

Jason B.Jason B.

50.5k33 gold badges9494 silver badges201201 bronze badges