# 十六进制字面量 十六进制字面量，以关键字`hex`打头，后面紧跟用单或双引号包裹的字符串。如`hex"001122ff"`。在内部会被表示为二进制流。通过下面的例子来理解下是什么意思： ``` pragma solidity ^0.4.0; contract HexLiteral{ function test() returns (string){ var a = hex"001122FF"; //var b = hex"A"; //Expected primary expression return a; } } ``` 由于一个字节是8位，所以一个`hex`是由两个`[0-9a-z]`字符组成的。所以`var b = hex"A";`不是成双的字符串是会报错的。 ## 转换 十六进制的字面量与字符串可以进行同样的类似操作： ``` pragma solidity ^0.4.0; contract HexLiteralBytes{ function test() returns (bytes4, bytes1, bytes1, bytes1, bytes1){ bytes4 a = hex"001122FF"; return (a, a[0], a[1], a[2], a[3]); } } ``` 可以发现，它可以隐式的转为`bytes`，上述代码的执行结果如下： ``` Result: "0x001122ff00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000011000000000000000000000000000000000000000000000000000000000000002200000000000000000000000000000000000000000000000000000000000000ff00000000000000000000000000000000000000000000000000000000000000" Transaction cost: 21857 gas. Execution cost: 585 gas. Decoded: bytes4: 0x001122ff bytes1: 0x00 bytes1: 0x11 bytes1: 0x22 bytes1: 0xff ```