Truffle compile compilation failed

Question

I am getting error while compiling a smart contract:

sudo truffle compile

Compiling ./contracts/Hello-world.sol...

Compiling ./contracts/Migrations.sol...


/home/user/truffle/contracts/Hello-world.sol:1:1: SyntaxError: Source file requires different compiler version (current compiler is 0.5.0+commit.1d4f565a.Emscripten.clang - note that nightly builds are considered to be strictly less than the released version

pragma solidity 0.4.15;

^----------------------^

Compilation failed. See above.

Truffle v5.0.2 (core: 5.0.2)

Node v8.10.0

Answer 1

This is a version compatibility problem. In your code you have mentioned to use version 0.4.15 but the compiler version installed in your system is 0.5.0 (mentioned in the error). There are two solutions to this.

1. Use the current version pragma solidity 0.5.0; 
2. Use pragma solidity ^0.4.15;

Note: 

pragma solidity 0.4.15; is mentioned to use the exact version whereas pragma solidity ^0.4.15; is mentioned to use the mentioned version and the above versions

Comments

^0.4.15 means >= 0.4.15 and < 0.5.0

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More specifically, 

^0.4.15 means >=0.4.15 and <= latest version