while loop to repeat when condition
while evaluates an expression,
and repeats the execution of a group of statements in a loop while
the expression is true. An expression is true when its result is nonempty
and contains only nonzero elements (logical or real numeric). Otherwise,
the expression is false.
while loop to calculate
n = 10; f = n; while n > 1 n = n-1; f = f*n; end disp(['n! = ' num2str(f)])
n! = 3628800
Count the number of lines of code in the file
magic.m. Skip blank lines and comments using a
continue skips the remaining instructions in the
while loop and begins the next iteration.
fid = fopen('magic.m','r'); count = 0; while ~feof(fid) line = fgetl(fid); if isempty(line) || strncmp(line,'%',1) || ~ischar(line) continue end count = count + 1; end count
count = 34
Sum a sequence of random numbers until the next random number is greater than an upper limit. Then, exit the loop using a
limit = 0.8; s = 0; while 1 tmp = rand; if tmp > limit break end s = s + tmp; end
An expression can include relational operators
==) and logical
operators (such as
~). Use the logical operators
create compound expressions. MATLAB® evaluates compound expressions
from left to right, adhering to operator precedence rules.
Within the conditional expression of a
as short-circuit operators. This behavior is the same as
short-circuit in conditional expressions and statements, it is good
practice to use
| within the expression.
x = 42; while exist('myfunction.m','file') && (myfunction(x) >= pi) disp('Expressions are true') break end
The first part of the expression evaluates to false. Therefore, MATLAB does not need to evaluate the second part of the expression, which would result in an undefined function error.
If you inadvertently create an infinite loop (that is, a loop that never ends on its own), stop execution of the loop by pressing Ctrl+C.
If the conditional expression evaluates to a matrix, MATLAB evaluates
the statements only if all elements in the matrix are true (nonzero).
To execute statements if any element is true, wrap the expression
When nesting a number of
while statement requires an
while loop is similar to a
in other programming languages, such as C and C++. However,
while evaluates the conditional expression at the
beginning of the loop rather than the
do % Not valid MATLAB syntax statements while expression
To mimic the behavior of a
do...while loop, set the initial
true and place the
conditional expression inside the loop. For example, implement the
do...while loop above by using a MATLAB
while true statements if ~expression break end end