Info Catalog octave: The switch Statement octave: Statements octave: The do-until Statement

octave: The while Statement

 
 10.3 The while Statement
 ========================
 
 In programming, a “loop” means a part of a program that is (or at least
 can be) executed two or more times in succession.
 
    The ‘while’ statement is the simplest looping statement in Octave.
 It repeatedly executes a statement as long as a condition is true.  As
 with the condition in an ‘if’ statement, the condition in a ‘while’
 statement is considered true if its value is nonzero, and false if its
 value is zero.  If the value of the conditional expression in a ‘while’
 statement is a vector or a matrix, it is considered true only if it is
 non-empty and _all_ of the elements are nonzero.
 
    Octave’s ‘while’ statement looks like this:
 
      while (CONDITION)
        BODY
      endwhile
 
 Here BODY is a statement or list of statements that we call the “body”
 of the loop, and CONDITION is an expression that controls how long the
 loop keeps running.
 
    The first thing the ‘while’ statement does is test CONDITION.  If
 CONDITION is true, it executes the statement BODY.  After BODY has been
 executed, CONDITION is tested again, and if it is still true, BODY is
 executed again.  This process repeats until CONDITION is no longer true.
 If CONDITION is initially false, the body of the loop is never executed.
 
    This example creates a variable ‘fib’ that contains the first ten
 elements of the Fibonacci sequence.
 
      fib = ones (1, 10);
      i = 3;
      while (i <= 10)
        fib (i) = fib (i-1) + fib (i-2);
        i++;
      endwhile
 
 Here the body of the loop contains two statements.
 
    The loop works like this: first, the value of ‘i’ is set to 3.  Then,
 the ‘while’ tests whether ‘i’ is less than or equal to 10.  This is the
 case when ‘i’ equals 3, so the value of the ‘i’-th element of ‘fib’ is
 set to the sum of the previous two values in the sequence.  Then the
 ‘i++’ increments the value of ‘i’ and the loop repeats.  The loop
 terminates when ‘i’ reaches 11.
 
    A newline is not required between the condition and the body; but
 using one makes the program clearer unless the body is very simple.
 

Info Catalog octave: The switch Statement octave: Statements octave: The do-until Statement