Using conditional breakpoints to print out value

3 次查看（过去 30 天）
Eric Sampson
Eric Sampson 2013-2-11
Hi, I'm interested if it would be possible to use/abuse(?) conditional breakpoints to print out the value of a variable to the command window. Sometimes I work with a codebase that is read-only, so I can't insert 'disp()' statements... Thanks!

请先登录，再回答此问题。

采纳的回答

Jonathan Sullivan
Jonathan Sullivan 2013-2-12
Yes sir. It takes a bit of creativity.
Here's an example. Let's print out "Hi" each time mod(ii,2) == 0.
iff(mod(ii,2),fprintf('Hi.\n') > 0,false)
This will pause the code execution. If you prefer to not pause the code execusion, try:
iff(mod(ii,2),fprintf('Hi.\n') == NaN,false)
Where iff is defined as follows:
function out = iff(cond,vtrue,vfalse)
if cond
out = vtrue;
else
out = vfalse;
end
  10 个评论
显示 8更早的评论
Sean de Wolski
Sean de Wolski 2013-2-12
So that it evaluates the anonymous function; that makes sense.
Eric Sampson
Eric Sampson 2013-2-12
Actually here's a pretty clean way to do it without requiring the IIF function, it relies on the short-circuting behavior of the AND operator to only execute the FPRINTF when the first expression is true - just put this as the breakpoint conditional expression:
mod(i,2) && (fprintf('test.\n') < 0) % or use >=0 if you want it to pause.

请先登录，再进行评论。

更多回答（2 个）

per isakson
per isakson 2013-2-12
编辑：per isakson 2013-2-12
Yes, that is possible. See tracer4m in the file exchange.
The function invoked at the conditional break point shall always return true and not error. Printing should be fine. If the name of variable isn't known beforehand one may use whos/who.
Matt J
Matt J 2013-2-11
编辑：Matt J 2013-2-11
Once the code stops at breakpoint, you can highlight a variable or expression in the editor window. Then right-click and select "Evaluate Selection".
You should also be able to see the value of a variable by hovering the mouse over any occurrence of it in the editor.
  1 个评论
Eric Sampson
Eric Sampson 2013-2-12
Hi Matt, yup I understand what you say - but I'm looking to have the variable's value printed to the command window each time that the condition is true (like a trace or log), without having to manually inspect the value each time. Cheers :)

请先登录，再进行评论。

类别

在 Help Center 和 File Exchange 中查找有关 Environment and Settings 的更多信息

标签

产品

Community Treasure Hunt

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

Start Hunting!

Translated by