What do the empty square brackets [] do in the expression executed by eval?

37 次查看（过去 30 天）
Geoff Inge
Geoff Inge 2019-9-5
编辑： Guillaume 2019-9-5
sys = eval([model '(0,[],[],''compile'')']);

请先登录，再回答此问题。

采纳的回答

Stephen23
Stephen23 2019-9-5
编辑：Stephen23 2019-9-5
"What do the empty square brackets [] do in the expression executed by eval?"
Nothing really.
MATLAB has positional input arguments. Many MATLAB functions use an empty numeric array (i.e. []) to indicate that an input argument is undefined, which allows further input arguments to be specified. In your example the 2nd and 3rd arguments are undefined, whilst the 1st and 4th arguments have defined values (i.e. 0 and the char vector 'compile' respectively).
That is all.
Read the function/model documentation to know if [] is accepted as an undefined positional input argument.
This has nothing to do with eval.

更多回答（1 个）

Guillaume
Guillaume 2019-9-5
编辑：Guillaume 2019-9-5
The same as they always do, concatenate whatever is inside the bracket. model must contain a char vector, so it just appends (0, [], [], 'compile') to whatever is in model.
A much better way of doing the same:
sys = feval(model, 0, [], [], 'compile');
don't use eval!
edit: completely misread the question. As Stephen explains, the brackets inside the call are used to tell the function called by eval to use the default value for that particular input.

类别

在 Help Center 和 File Exchange 中查找有关 Simulink 的更多信息

标签

产品


版本

R2018b

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by