跨平台freebasic集锦(2)-基本语法（1）-dim(1)

dim

例子

dim x as integer
dim y as integer
DIM  z1 as integer
dim z2 as integer
dim userName as string
x=5
y=8
z1=x+y
z2=x-y
Print "x = "; x
Print "y = "; y
Print "z1:"; z1;"   z2:",z2

编译并运行

F:\learn\fbs>1
x =  5
y =  8
z1: 13   z2:  -3F:\learn\fbs>

dim x as integer
dim y as integer
DIM  as integer z1,z2 
dim userName as string
x=5
y=8
z1=x+y
z2=x-y
Print "z1:"; z1;"   z2:",z2
userName="张三"
print "你好";userName

F:\learn\fbs>1
z1: 13   z2:  -3
你好张三F:\learn\fbs>

DIM

语法


Dim [Shared] name1 As DataType [, name2 As DataType, ...]
或
Dim [Shared] As DataType name1 [, name2, ...]

数组

Dim name ( [lbound To] ubound [, ...] ) As DataType
Dim name ( Any [, Any...] ) As DataType
Dim name ( ) As DataType

初始化

Dim scalar_symbol As DataType = expression | Any
Dim array_symbol (arraybounds) As DataType = { expression [, ...] } | Any
Dim udt_symbol As DataType = ( expression [, ...] ) | Any

按名称声明变量并保留内存以容纳它。

变量必须先声明，然后才能在-lang fb方言中使用，或者在其他方言中使用Option Explicit。只有在-lang qb和-lang fblite方言中，可以在不首先声明变量的情况下使用变量，在这种情况下，它们被称为隐式变量。

Dim可用于声明和分配任何受支持数据类型、用户定义类型或枚举的变量。

根据变量或数组的声明位置和方式，可以更改其在内存中的分配方式。请参阅存储类别。

通过用逗号分隔每个变量声明，可以在单个Dim语句中声明多个变量。
比如

'' Variable declaration examples'' One variable per DIM statement
Dim text As String
Dim x As Double'' More than one variable declared, different data types
Dim k As Single, factor As Double, s As String'' More than one variable declared, all same data types
Dim As Integer mx, my, mz ,mb'' Variable having an initializer
Dim px As Double Ptr = @x

具有隐式数据类型的显式变量

在-lang qb和-lang fblite方言中，即使变量是显式声明的，如果数据类型不是通过名称或类型后缀显式给出的，也将为其提供默认数据类型。默认数据类型在-lang qb方言中为Single，在-lang fblite方言中为Integer。通过使用Def###语句，可以在整个源列表中更改默认数据类型。（例如，DefInt、DefStr、DefSng）


'' Compile with -lang qb'$lang: "qb"'' All variables beginning with A through N will default to the INTEGER data type
'' All other variables default to the SINGLE data type
DefInt I-NDim I, J, X, Y, T$, D As Double
'' I and J are INTEGERs
'' X and Y are SINGLEs
'' T$ is STRING
'' D is DOUBLE

数组

与大多数BASIC方言一样，FreeBASIC支持索引范围从下限到上限的数组。在所示的语法中，lbound指的是下限或最小索引。ubound是指上限，或最大的索引。如果未指定下限，则默认为零，除非使用Option Base。

Const upperbound = 10'' Declare an array with indexes ranging from 0 to upperbound,
'' for a total of (upperbound + 1) indexes.
Dim array(upperbound) As Single

多维数组

多维数组也可以声明，并以这种确定的顺序存储：仅在最后一个索引中不同的值是连续的（行主顺序）。

多维数组的最大维数为8。

'' declare a three-dimensional array of single
'' precision floating-point numbers.
Dim array(1 To 2, 6, 3 To 5) As Single'' The first dimension of the declared array
'' has indices from 1 to 2, the second, 0 to 6,
'' and the third, 3 to 5.