MATLAB Answers

# Multiple conditions for while loop.

218 views (last 30 days)
Ahmad on 18 Apr 2016
Commented: Shaarif Dilshad on 13 Jan 2021 at 15:29
while (Ea0 >= 0.01)&&(Ea0 >= 0.01)||(Sr >= 10^-4)
This loop keeps on going even though the first part
(Ea0 >= 0.01)&&(Ea1 >= 0.01)
is met i.e. Ea0 and Ea1 dipped below 0.01, why is that?
I want it to stop if
(Ea0 >= 0.01)&&(Ea0 >= 0.01)
or
(Sr >= 10^-4)
are met! Thanks in advance!

#### 0 Comments

Sign in to comment.

### Answers (1)

Joachim Schlosser on 18 Apr 2016
Error 1: You wrote Ea0 two times, but surely meant to write Ea1 in the second sub expression.
Error 2: Since the && is evaluated before '||, your loop will only end if both sides are false.
What you are describing above is another expression, where you want all sub expressions to hold true for the loop to continue:
while ((Ea0 >= 0.01) || (Ea1 >= 0.01)) && (Sr >= 10^-4)
Note the extra parens around the EaX expressions to specify that both must fail for the loop to end. If you want any sub expression to end the loop, replace '|| again by &&.

#### 3 Comments

Stephen Cobeldick on 18 Apr 2016
Ahmad's "Answer" moved here:
thank u for ur reply but i'm confused! sorry I meant Ea1 yeah!
ur syntax work, although I don't understand it!
how is while ((Ea0 >= 0.01) vertical slash vertical slash (Ea1 >= 0.01)) && (Sr >= 10^-4) equal to (Ea0 >= 0.01)&&(Ea1 >= 0.01)" or "(Sr >= 10^-4) "
Joachim Schlosser on 18 Apr 2016
:-) It is not, that's why it works.
The while loop does not take an expression describing the abortion prerequisites, but those for continuation. So effectively you have to turn your thoughts around and describe what has to be true to continue.
You may want to learn about Conjunctive Normal Form to understand how to move between the two thought models.
Shaarif Dilshad on 13 Jan 2021 at 15:29
if we write 2 times end then this is an error

Sign in to comment.

### Community Treasure Hunt

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

Start Hunting!

Translated by