For the while loop in MATLAB®, see
This functionality does not run in MATLAB.
while - end_while represents a loop that
evaluates its body while a specified condition holds true.
evaluated before the body is executed for the first time. If
the loop is entered and
condition evaluates to
The body can consist of any number of statements which must
be separated either by a colon
: or a semicolon
Only the last evaluated result inside the body (the return value of
the loop) is printed on the screen. Use
end_while can be replaced by
The imperative form
while - end_while is
equivalent to corresponding call of the function
In most cases, the imperative form leads to simpler code.
is often a more elegant notation for loops.
_while is a function of the system kernel.
while loops do not show intermediate results
of statements within a loop:
i := 1: s := 0: while i < 3 do s := s + i; i := i + 1; end_while
i := 1: s := 0: while i < 3 do print("intermediate sum" = s); s := s + i; i := i + 1; s end_while
delete i, s:
Express the same statements as a
and as an equivalent
while loop. In more complicated
cases, you might need additional initializations of variables:
i := 1: repeat print(i); i := i + 1; until i = 3 end:
i := 1: while i < 3 do print(i); i := i + 1; end:
condition := UNKNOWN: while not condition do print(Condition = condition); condition := TRUE; end_while:
Error: The Boolean 'TRUE' or 'FALSE' is expected. [while]
To avoid this error, change the stopping criterion to
condition := UNKNOWN: while condition <> TRUE do print(Condition = condition); condition := TRUE; end_while:
You also can create a
while loop by using
the functional form
hold(_while(condition, (statement1; statement2)))
while condition do statement1; statement2 end_while
The body of the loop: an arbitrary sequence of statements
Value of the last command executed in the body of the loop.
If no command was executed, the value
NIL is returned. If the body of a
is not evaluated due to a false condition, the void object of type