假定大小的数组：科隆主场迎战星号 - DIMENSION（:) ARR与ARR（*） [英] Assumed size arrays: Colon vs. asterisk - DIMENSION(:) arr vs. arr(*)

问题描述

是否有声明假定大小的数组的这两种方法有什么区别？

例如。

 真实的，尺寸（:) :: ARR
 

和

 真正:: ARR（*）
 

解决方案

形式

 真实的，尺寸（:) :: ARR
 

声明了一个假定形状阵列，而形式

 真正:: ARR（*）
 

声明了一个假定大小阵列。

和，是的，有使用它们之间的差异。的差异的产生是因为，大约，编译器知道的假定形状阵列的形状，但不是假定大小阵列。提供给编译器的额外信息是指，除其他事项外，假定形状阵列可在整个阵列的前pressions使用。假定大小的数组只能在整个阵列前pressions时使用它在不需要数组的形状的过程引用的实际参数。哦，还有到内在 LBOUND 通话 - 在呼叫而不是内在 UBOUND 。还有其他一些微妙的，不那么微妙，差异，你的标准还是不错的Fortran书细读就会发现。

的几点建议对新的Fortran编程是可能时使用假定形状数组。他们不是用Fortran 90的前，所以你会看到很多老code假定大小数组。假定形状阵列是在新的code更好，因为形状和大小的功能可以用来查询它们的大小，以避免外的边界错误并ALLOCATE阵列，其尺寸取决于输入阵列的尺寸。

Is there any difference between these two methods of declaring an assumed-size array?

e.g.

real, dimension(:) :: arr

and

real               :: arr(*)

解决方案

The form

real, dimension(:) :: arr

declares an assumed-shape array, while the form

real :: arr(*)

declares an assumed-size array.

And, yes, there are differences between their use. The differences arise because, approximately, the compiler 'knows' the shape of the assumed-shape array but not of the assumed-size array. The extra information available to the compiler means that, among other things, assumed-shape arrays can be used in whole-array expressions. An assumed-size array can only be used in whole array expressions when it's an actual argument in a procedure reference that does not require the array's shape. Oh, and also in a call to the intrinsic lbound -- but not in a call to the intrinsic ubound. There are other subtle, and not-so-subtle, differences which your close reading of the standard or of a good Fortran book will reveal.

Some advice for new Fortran programmers is to use assumed-shape arrays when possible. They were not available before Fortran 90, so you will see lots of assumed-size arrays in old code. Assumed-shape arrays are better in new code, because the SHAPE and SIZE functions can be used to query their sizes to avoid out-of-bounds error and to ALLOCATE arrays whose dimensions depend on the dimensions of input arrays.

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