|MATLAB Function Reference|
Repeat statements an indefinite number of times
statements an indefinite number of times. The
statements are executed while the real part of
expression has all nonzero elements.
expression is usually of the form
rel_op is ==, <, >, <=, >=, or ~=.
The scope of a
while statement is always terminated with a matching
expression is a MATLAB expression, usually consisting of variables or smaller expressions joined by relational operators
count < limit), or logical functions (e.g.,
Simple expressions can be combined by logical operators (
~) into compound expressions such as the following. MATLAB evaluates compound expressions from left to right, adhering to operator precedence rules.
statements is one or more MATLAB statements to be executed only while the
true or nonzero.
If the evaluated
expression yields a nonscalar value, then every element of this value must be
true or nonzero for the entire expression to be considered
true. For example, the statement,
(A < B) is
true only if each element of matrix
A is less than its corresponding element in matrix
B. See Example 2, below.
Partial Evaluation of the Expression Argument
Within the context of an
while expression, MATLAB does not necessarily evaluate all parts of a logical expression. In some cases it is possible, and often advantageous, to determine whether an expression is
false through only partial evaluation.
For example, if
A equals zero in statement 1 below, then the expression evaluates to
false, regardless of the value of
B. In this case, there is no need to evaluate
B and MATLAB does not do so. In statement 2, if
A is nonzero, then the expression is
true, regardless of
B. Again, MATLAB does not evaluate the latter part of the expression.
You can use this property to your advantage to cause MATLAB to evaluate a part of an expression only if a preceding part evaluates to the desired state. Here are some examples.
Example 1 - Simple while Statement
eps is a tolerance used to determine such things as near singularity and rank. Its initial value is the machine epsilon, the distance from 1.0 to the next largest floating-point number on your machine. Its calculation demonstrates
Example 2 - Nonscalar Expression