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For some reason solidity doesn't allow to push values into memory array

Member "push" is not available in bytes32[] memory outside of storage.

Here is sample contract code:

pragma solidity ^0.4.21;

contract Foo {
    function getRange(uint n) public pure returns(uint[]) {
        uint[] memory result;
        for (uint i = 0; i < n; i++)
            if (someCondition(i))
               result.push(i);
        return result;
    }
}

I could allocate maximum possible array of size n and then shrink it, but it may hurt performance (n could be in order of magnitude of 100000 while final length of result is 0..100). For example, someCondition could be isPrime. In this case we have large N (which makes impossible to preallocate an array) and small list of resulting prime numbers.

How could it be done?

I ended up with preallicating array of size n and then shrinking it once I know it's final length:

function getRange(uint n) public pure returns(uint[]) {
    uint tookCount = 0;
    uint[] memory result;
    for (uint i = 0; i < n; i++)
        if (someCondition(i)) {
            result.push(i);
            tookCount++;
        }
           
    uint[] memory trimmedResult = new uint[](tookCount);
    for (uint j = 0; j < trimmedResult.length; j++) {
        trimmedResult[j] = result[j];
    }
    return trimmedResult;
}

For some reason solidity doesn't allow to push values into memory array

Member "push" is not available in bytes32[] memory outside of storage.

Here is sample contract code:

pragma solidity ^0.4.21;

contract Foo {
    function getRange(uint n) public pure returns(uint[]) {
        uint[] memory result;
        for (uint i = 0; i < n; i++)
            if (someCondition(i))
               result.push(i);
        return result;
    }
}

I could allocate maximum possible array of size n and then shrink it, but it may hurt performance (n could be in order of magnitude of 100000 while final length of result is 0..100). For example, someCondition could be isPrime. In this case we have large N (which makes impossible to preallocate an array) and small list of resulting prime numbers.

How could it be done?

I ended up with preallicating array of size n and then shrinking it once I know it's final length:

function getRange(uint n) public pure returns(uint[]) {
    uint tookCount = 0;
    uint[] memory result = new uint[](n);
    for (uint i = 0; i < n; i++)
        if (someCondition(i)) {
            result.push(i);
            tookCount++;
        }
           
    uint[] memory trimmedResult = new uint[](tookCount);
    for (uint j = 0; j < trimmedResult.length; j++) {
        trimmedResult[j] = result[j];
    }
    return trimmedResult;
}

For some reason solidity doesn't allow to push values into memory array

Member "push" is not available in bytes32[] memory outside of storage.

Here is sample contract code:

pragma solidity ^0.4.21;

contract Foo {
    function getRange(uint n) public pure returns(uint[]) {
        uint[] memory result;
        for (uint i = 0; i < n; i++)
            if (someCondition(i))
               result.push(i);
        return result;
    }
}

I could allocate maximum possible array of size n and then shrink it, but it may hurt performance (n could be in order of magnitude of 100000 while final length of result is 0..100). For example, someCondition could be isPrime. In this case we have large N (which makes impossible to preallocate an array) and small list of resulting prime numbers.

How could it be done?

For some reason solidity doesn't allow to push values into memory array

Member "push" is not available in bytes32[] memory outside of storage.

Here is sample contract code:

pragma solidity ^0.4.21;

contract Foo {
    function getRange(uint n) public pure returns(uint[]) {
        uint[] memory result;
        for (uint i = 0; i < n; i++)
            if (someCondition(i))
               result.push(i);
        return result;
    }
}

I could allocate maximum possible array of size n and then shrink it, but it may hurt performance (n could be in order of magnitude of 100000 while final length of result is 0..100). For example, someCondition could be isPrime. In this case we have large N (which makes impossible to preallocate an array) and small list of resulting prime numbers.

How could it be done?

I ended up with preallicating array of size n and then shrinking it once I know it's final length:

function getRange(uint n) public pure returns(uint[]) {
    uint tookCount = 0;
    uint[] memory result;
    for (uint i = 0; i < n; i++)
        if (someCondition(i)) {
            result.push(i);
            tookCount++;
        }
           
    uint[] memory trimmedResult = new uint[](tookCount);
    for (uint j = 0; j < trimmedResult.length; j++) {
        trimmedResult[j] = result[j];
    }
    return trimmedResult;
}

For some reason solidity doesn't allow to push values into memory array

Member "push" is not available in bytes32[] memory outside of storage.

Here is sample contract code:

pragma solidity ^0.4.21;

contract Foo {
    function getRange(uint n) public pure returns(uint[]) {
        uint[] memory result;
        for (uint i = 0; i < n; i++)
            result.push(i);
        return result;
    }
}

How could it be done?

For some reason solidity doesn't allow to push values into memory array

Member "push" is not available in bytes32[] memory outside of storage.

Here is sample contract code:

pragma solidity ^0.4.21;

contract Foo {
    function getRange(uint n) public pure returns(uint[]) {
        uint[] memory result;
        for (uint i = 0; i < n; i++)
            if (someCondition(i))
               result.push(i);
        return result;
    }
}

I could allocate maximum possible array of size n and then shrink it, but it may hurt performance (n could be in order of magnitude of 100000 while final length of result is 0..100). For example, someCondition could be isPrime. In this case we have large N (which makes impossible to preallocate an array) and small list of resulting prime numbers.

How could it be done?