Multiplication and iteration in solidity

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1
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Iteration uses a lot of gas. I was thinking at different options I could minimise the costs. I must understand why one thing doesn't work:
Why can't I push into an array using multiplication rather than loops?

For example, this code works:

address contenders

for (int i; i<5;i++)
 contenders.push(msg.sender);

This code doesn't:

address contenders
uint numberToMultiply /// let's say this variable is 5

contenders.push(msg.sender) * numberToMultiply

Basically in the last example I am expecting to push msg.sender in the array by the number of times stored in the variable.

Would it not be gas efficient? Furthermore, it doesn't work. Does anyone know the reason?

solidity remix gas

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asked 5 hours ago

Cristian

546

add a comment | 

up vote
1
down vote

favorite

Iteration uses a lot of gas. I was thinking at different options I could minimise the costs. I must understand why one thing doesn't work:
Why can't I push into an array using multiplication rather than loops?

For example, this code works:

address contenders

for (int i; i<5;i++)
 contenders.push(msg.sender);

This code doesn't:

address contenders
uint numberToMultiply /// let's say this variable is 5

contenders.push(msg.sender) * numberToMultiply

Basically in the last example I am expecting to push msg.sender in the array by the number of times stored in the variable.

Would it not be gas efficient? Furthermore, it doesn't work. Does anyone know the reason?

solidity remix gas

share|improve this question

asked 5 hours ago

Cristian

546

add a comment | 

up vote
1
down vote

favorite

up vote
1
down vote

favorite

Iteration uses a lot of gas. I was thinking at different options I could minimise the costs. I must understand why one thing doesn't work:
Why can't I push into an array using multiplication rather than loops?

For example, this code works:

address contenders

for (int i; i<5;i++)
 contenders.push(msg.sender);

This code doesn't:

address contenders
uint numberToMultiply /// let's say this variable is 5

contenders.push(msg.sender) * numberToMultiply

Basically in the last example I am expecting to push msg.sender in the array by the number of times stored in the variable.

Would it not be gas efficient? Furthermore, it doesn't work. Does anyone know the reason?

solidity remix gas

share|improve this question

asked 5 hours ago

Cristian

546

Iteration uses a lot of gas. I was thinking at different options I could minimise the costs. I must understand why one thing doesn't work:
Why can't I push into an array using multiplication rather than loops?

For example, this code works:

address contenders

for (int i; i<5;i++)
 contenders.push(msg.sender);

This code doesn't:

address contenders
uint numberToMultiply /// let's say this variable is 5

contenders.push(msg.sender) * numberToMultiply

Basically in the last example I am expecting to push msg.sender in the array by the number of times stored in the variable.

Would it not be gas efficient? Furthermore, it doesn't work. Does anyone know the reason?

solidity remix gas

solidity remix gas

share|improve this question

asked 5 hours ago

Cristian

546

share|improve this question

asked 5 hours ago

Cristian

546

share|improve this question

share|improve this question

asked 5 hours ago

Cristian

546

asked 5 hours ago

Cristian

546

asked 5 hours ago

Cristian

546

546

add a comment | 

add a comment | 

2 Answers
2

active

oldest

votes

up vote
3
down vote



accepted

I'm not sure if that kind of construct would work in any language (none that I know of) but I also fail to see what would be the point. I can't see many situations where someone would want to push the same value multiple times into an array. Maybe something like initializing an array with all true boolean values.

Because commands are executed from left to right, the contenders.push(msg.sender) is executed first. It returns the new length of the array (What is the return of array.push() in Solidity?). Therefore you are trying to execute something like "number * 5", which actually should give you a result if you store it in a variable - but it's not executing anything except the calculation.

share|improve this answer

answered 4 hours ago

Lauri Peltonen

3,0531319

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  [OT] in Python you can write something like this a = [1]*27
  – Briomkez
  4 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  Exactly. It's because I'm coming from python so that's why I thought it would work this way. Thanks all for the answers. I make sure to leave a big up for you all
  – Cristian
  3 hours ago
  

  
  
  
  

add a comment | 

up vote
1
down vote

The code doesn't work because it was not designed to work that way. You are missing the concept.

From solidity documentation

push: Dynamic storage arrays and bytes (not string) have a member
function called push that can be used to append an element at the end
of the array. The function returns the new length.

Array.push return new length of the array. So multiplying it by 5 won't insert the data 5 times.

share|improve this answer

answered 4 hours ago

Prashant Prabhakar Singh

3,73631546

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Thanks for the information. I was thinking if the language had this functionality like Python but seems to not.
  – Cristian
  3 hours ago
  

  
  
  
  

add a comment | 

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2 Answers
2

active

oldest

votes

2 Answers
2

active

oldest

votes

active

oldest

votes

active

oldest

votes

up vote
3
down vote



accepted

I'm not sure if that kind of construct would work in any language (none that I know of) but I also fail to see what would be the point. I can't see many situations where someone would want to push the same value multiple times into an array. Maybe something like initializing an array with all true boolean values.

Because commands are executed from left to right, the contenders.push(msg.sender) is executed first. It returns the new length of the array (What is the return of array.push() in Solidity?). Therefore you are trying to execute something like "number * 5", which actually should give you a result if you store it in a variable - but it's not executing anything except the calculation.

share|improve this answer

answered 4 hours ago

Lauri Peltonen

3,0531319

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  [OT] in Python you can write something like this a = [1]*27
  – Briomkez
  4 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  Exactly. It's because I'm coming from python so that's why I thought it would work this way. Thanks all for the answers. I make sure to leave a big up for you all
  – Cristian
  3 hours ago
  

  
  
  
  

add a comment | 

up vote
3
down vote



accepted

I'm not sure if that kind of construct would work in any language (none that I know of) but I also fail to see what would be the point. I can't see many situations where someone would want to push the same value multiple times into an array. Maybe something like initializing an array with all true boolean values.

Because commands are executed from left to right, the contenders.push(msg.sender) is executed first. It returns the new length of the array (What is the return of array.push() in Solidity?). Therefore you are trying to execute something like "number * 5", which actually should give you a result if you store it in a variable - but it's not executing anything except the calculation.

share|improve this answer

answered 4 hours ago

Lauri Peltonen

3,0531319

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  [OT] in Python you can write something like this a = [1]*27
  – Briomkez
  4 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  Exactly. It's because I'm coming from python so that's why I thought it would work this way. Thanks all for the answers. I make sure to leave a big up for you all
  – Cristian
  3 hours ago
  

  
  
  
  

add a comment | 

up vote
3
down vote



accepted

up vote
3
down vote



accepted

I'm not sure if that kind of construct would work in any language (none that I know of) but I also fail to see what would be the point. I can't see many situations where someone would want to push the same value multiple times into an array. Maybe something like initializing an array with all true boolean values.

Because commands are executed from left to right, the contenders.push(msg.sender) is executed first. It returns the new length of the array (What is the return of array.push() in Solidity?). Therefore you are trying to execute something like "number * 5", which actually should give you a result if you store it in a variable - but it's not executing anything except the calculation.

share|improve this answer

answered 4 hours ago

Lauri Peltonen

3,0531319

I'm not sure if that kind of construct would work in any language (none that I know of) but I also fail to see what would be the point. I can't see many situations where someone would want to push the same value multiple times into an array. Maybe something like initializing an array with all true boolean values.

Because commands are executed from left to right, the contenders.push(msg.sender) is executed first. It returns the new length of the array (What is the return of array.push() in Solidity?). Therefore you are trying to execute something like "number * 5", which actually should give you a result if you store it in a variable - but it's not executing anything except the calculation.

share|improve this answer

answered 4 hours ago

Lauri Peltonen

3,0531319

share|improve this answer

share|improve this answer

answered 4 hours ago

Lauri Peltonen

3,0531319

answered 4 hours ago

Lauri Peltonen

3,0531319

answered 4 hours ago

Lauri Peltonen

3,0531319

3,0531319

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  [OT] in Python you can write something like this a = [1]*27
  – Briomkez
  4 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  Exactly. It's because I'm coming from python so that's why I thought it would work this way. Thanks all for the answers. I make sure to leave a big up for you all
  – Cristian
  3 hours ago
  

  
  
  
  

add a comment | 

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  [OT] in Python you can write something like this a = [1]*27
  – Briomkez
  4 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  Exactly. It's because I'm coming from python so that's why I thought it would work this way. Thanks all for the answers. I make sure to leave a big up for you all
  – Cristian
  3 hours ago
  

  
  
  
  

1

1

[OT] in Python you can write something like this a = [1]*27
– Briomkez
4 hours ago

[OT] in Python you can write something like this a = [1]*27
– Briomkez
4 hours ago

Exactly. It's because I'm coming from python so that's why I thought it would work this way. Thanks all for the answers. I make sure to leave a big up for you all
– Cristian
3 hours ago

Exactly. It's because I'm coming from python so that's why I thought it would work this way. Thanks all for the answers. I make sure to leave a big up for you all
– Cristian
3 hours ago

add a comment | 

up vote
1
down vote

The code doesn't work because it was not designed to work that way. You are missing the concept.

From solidity documentation

push: Dynamic storage arrays and bytes (not string) have a member
function called push that can be used to append an element at the end
of the array. The function returns the new length.

Array.push return new length of the array. So multiplying it by 5 won't insert the data 5 times.

share|improve this answer

answered 4 hours ago

Prashant Prabhakar Singh

3,73631546

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Thanks for the information. I was thinking if the language had this functionality like Python but seems to not.
  – Cristian
  3 hours ago
  

  
  
  
  

add a comment | 

up vote
1
down vote

The code doesn't work because it was not designed to work that way. You are missing the concept.

From solidity documentation

push: Dynamic storage arrays and bytes (not string) have a member
function called push that can be used to append an element at the end
of the array. The function returns the new length.

Array.push return new length of the array. So multiplying it by 5 won't insert the data 5 times.

share|improve this answer

answered 4 hours ago

Prashant Prabhakar Singh

3,73631546

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Thanks for the information. I was thinking if the language had this functionality like Python but seems to not.
  – Cristian
  3 hours ago
  

  
  
  
  

add a comment | 

up vote
1
down vote

up vote
1
down vote

The code doesn't work because it was not designed to work that way. You are missing the concept.

From solidity documentation

push: Dynamic storage arrays and bytes (not string) have a member
function called push that can be used to append an element at the end
of the array. The function returns the new length.

Array.push return new length of the array. So multiplying it by 5 won't insert the data 5 times.

share|improve this answer

answered 4 hours ago

Prashant Prabhakar Singh

3,73631546

The code doesn't work because it was not designed to work that way. You are missing the concept.

From solidity documentation

push: Dynamic storage arrays and bytes (not string) have a member
function called push that can be used to append an element at the end
of the array. The function returns the new length.

Array.push return new length of the array. So multiplying it by 5 won't insert the data 5 times.

share|improve this answer

answered 4 hours ago

Prashant Prabhakar Singh

3,73631546

share|improve this answer

share|improve this answer

answered 4 hours ago

Prashant Prabhakar Singh

3,73631546

answered 4 hours ago

Prashant Prabhakar Singh

3,73631546

answered 4 hours ago

Prashant Prabhakar Singh

3,73631546

3,73631546

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Thanks for the information. I was thinking if the language had this functionality like Python but seems to not.
  – Cristian
  3 hours ago
  

  
  
  
  

add a comment | 

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Thanks for the information. I was thinking if the language had this functionality like Python but seems to not.
  – Cristian
  3 hours ago
  

  
  
  
  

Thanks for the information. I was thinking if the language had this functionality like Python but seems to not.
– Cristian
3 hours ago

Thanks for the information. I was thinking if the language had this functionality like Python but seems to not.
– Cristian
3 hours ago

add a comment | 

 

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