Eric-
Here is the for loop I was having trouble with (I had to recreate it
from memory.)
article: make block! 50
article: load %news.txt
article_length: length? article
news_page: make string! 1000
paragraph_begin: make tag! <P>
paragraph_end: make tag! </P>
for add_tags 3 article_length 1 [
paragraph_with_tags: join paragraph_begin [ article add_tags ]
paragraph_end
append news_page paragraph_with_tags
]
>
>Hi Ryan,
>
>Could you show me some code where you've had trouble? I'm not aware of
any
>documentation other than the User's Guide and what you get by using
HELP.
>I've found that most of my problems with the loop functions are solved
by
>realizing that they are just functions that take arguments, and that
you have
>to pay close attention to how the arguments you feed them are going to
look.
>
>>> ? while
>While a condition block is TRUE, evaluates another block.
>Arguments:
> cond-block -- (block)
> body-block -- (block)
>
>WHILE takes two block arguments. The first one is repeatedly
evaluated, and
>as long as that evaluation returns a true value, the second one is
also
>evaluated.
>
>>> ? for
>Repeats a block over a range of values.
>Arguments:
> word -- Variable to hold current value (word)
> start -- Starting value (number series money time date char)
> end -- Ending value (number series money time date char)
> bump -- Amount to skip each time (number money time char)
> body -- Block to evaluate (block)
>
>FOR takes five arguments! I'm always getting the number wrong, and the
error
>messages are always confusing. Basically what you want is a word,
three
>numbers, then the block to be evaluated.
>
>And so on ... Now why would your FOR statement ignore part of your
block?
>Perhaps there's an if statement that's not right. Perhaps you have a
block
>within your FOR block that you expect to be evaluated, but it's just
sitting
>there because it's not the argument of an IF or a LOOP or a TRY or a
DO or a
>... Perhaps you're trying to use a word argument of FOR or FOREACH
after
>you've exited from the FOR or FOREACH block.
>
>>> for x 0 4 1 [print x]
>0
>1
>2
>3
>4
>>> print x
>** Script Error: x has no value.
>** Where: print x
>
>X here is strictly local to the FOR block. It looses its value once
you leave
>that block. In such a case you should do:
>
>>> x: 0 while [x <= 4][print x x: x + 1]
>0
>1
>2
>3
>4
>== false
>>> print x
>5
>
>Finally, since REBOL code uses no delimiters for their own sake, if
get the
>number of arguments to one function wrong, the error may show up some
place
>where you'd never expect. You've got to keep looking at the help for
the
>functions you use, and keep your code formatted to make it as
transparent as
>possible how everything should evaluate out.
>
>Good luck!
>Eric
>
>
