跳到主要内容

Expression

In programming languages expression is a unit of code which returns a value, in Move, almost everything is an expression, - with the sole exception of let statement which is a declaration. In this section, we cover the types of expressions and introduce the concept of scope.

Expressions are sequenced with semicolons ;. If there's "no expression" after the semicolon, the compiler will insert a unit () - an empty expression.

Literals​

In the Primitive Types section, we introduced the basic types of Move. And to illustrate them, we used literals. A literal is a notation for representing a fixed value in the source code. Literals are used to initialize variables and to pass arguments to functions. Move has the following literals:

  • true and false for boolean values
  • 0, 1, 123123 or other numeric for integer values
  • 0x0, 0x1, 0x123 or other hexadecimal for integer values
  • b"bytes_vector" for byte vector values
  • x"0A" HEX literal for byte values

Operators​

Arithmetic, logical, and bitwise operators are used to perform operations on values. The result of an operation is a value, so operators are also expressions.

Blocks​

A block is a sequence of statements and expressions, and it returns the value of the last expression in the block. A block is written as a pair of curly braces {}. A block is an expression, so it can be used anywhere an expression is expected.

Function Calls​

We go into detail about functions in the Functions section. However, we already used function calls in the previous sections, so it's worth mentioning them here. A function call is an expression that calls a function and returns the value of the last expression in the function body.

Control Flow Expressions​

Control flow expressions are used to control the flow of the program. They are also expressions, so they return a value. We cover control flow expressions in the Control Flow section. Here's a very brief overview: