Parameter function in Solidity

Question

I am a newbie in Solidity. Below is the snippet of code I came across :-

pragma solidity ^0.4.0; contract C {                                           //1
    function f(uint len) {                 // value passed to len = 7          //2 
        uint[] memory a = new uint[](7);                                       //3
        bytes memory b = new bytes(len);                                       //4    
// Here we have a.length == 7 and b.length == len a[6] = 8;                     // 5    
}
}

I am unable to understand why (7) is written after new uint[] in RHS of line 3. Moreover bytes is a data type of fixed length i.e bytes1 , then how did they created a new instance of it with length equal to len . At last what is meant by this b.length == len a[6] = 8 in line 5 .

Answer 1

I am unable to understand why (7) is written after new unit[]

This Is just another way to define fixed arrays.

Moreover bytes is a data type of fixed length i.e bytes1

From my experience and with the help of this article I can say that bytes can be of various lengths. And the len will be the user input.

b.length == len a[6] = 8

I think this comment is written wrong, it should've been something like this:

b.length == len,  a[6] = 8

A comma , is missing I think. If we put the comma then it makes more sense. So now it just means that b's array length will be equal to len which will be the input.

I hope you'll find this helpful