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This topic is about Solidity – Pure Functions.

Pure functions ensure that they not read or modify the state. A function can be declared as pure. The following statements if present in the function are considered reading the state and compiler will throw warning in such cases.

• Reading state variables.
• Accessing address(this).balance or <address>.balance.
• Accessing any of the special variable of block, tx, msg (msg.sig and msg.data can be read).
• Calling any function not marked pure.
• Using inline assembly that contains certain opcodes.

Pure functions can use the revert() and require() functions to revert potential state changes if an error occurs.

See the example below using a view function.

Example

pragma solidity ^0.5.0;

contract Test {
   function getResult() public pure returns(uint product, uint sum){
      uint a = 1; 
      uint b = 2;
      product = a * b;
      sum = a + b; 
   }
}

Run the above program using steps provided in Solidity First Application chapter.

Output

0: uint256: product 2
1: uint256: sum 3

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