Fibonacci series

[leke]

I have been learning the WHILE loop in REBOL. The only examples in the Core Guide seem to use it in series like this:

    colors: [red green blue yellow orange]

    while [not tail? colors] [
        print first colors
        colors: next colors
    ]

    red
    green
    blue
    yellow
    orange

Could any one give me a REBOL version of this peice of code:
 
>>> a, b = 0, 1
>>> while b < 10:
...       print b
...       a, b = b, a+b

I tried:

REBOL []
a: 0
b: 1
while [b < 100]
[print b
   a: b      
   b: a + b]

halt

but this is wrong somehow.
It's meant to print out the Fibonacci series
 

[DideC]

The problem is on 'a

In the pseudo code you try to implement, you affect 2 values to two vars in one line :

... a, b = b, a+b

But the Rebol code you post doesn't do that :

a: b
b: a + b]

As the 'b value is affected to 'a, you have a = b and the last line mean b: b + b

You can solve the problem by picking the 'a value and affecting the 'b value to it just after, all this in the 'b computation :

Code:

Rebol []
a: 0
b: 1
while [b < 100] [
print b
b: a + a: b
]

[RebolBert]

Could any one give me a REBOL version of this peice of code:
 
>>> a, b = 0, 1
>>> while b < 10:
...       print b
...       a, b = b, a+b

Yes :

Code:

set [a b] [0 1]
while [b < 10] [
    print b
    set [a b] reduce [b  a + b]
]