I dare say this one will get me into trouble...
At 9:36 PM -0500 25/7/05, [EMAIL PROTECTED] wrote:
For me, the biggest problem I have with the docs, aside from not being
able to find things, is that when I get to a topic, there are not enough
examples to indicate exactly how a facility might be used. Whether this
belongs in the "docs" or in something else is beside the point. If I'm
struggling with how to use a REPEAT, I need examples.
Here is some help with repeat that includes no less than 8 code
examples. You can find many, many more examples of how and when to
use repeat in almost any Rev project that you care to open and
examine. I hope that helps (HTH).
I'm sorry if this post is excessively long. It is Jeanne's fault for
writing a long dictionary entry ;-)
From the docs:
repeat control structure
Platform support:
Introduced in version 1.0 (Changed in version 2.0)
Executes a set of statements repeatedly.
repeat loopForm
statementList
end repeat
See also: each keyword, end repeat keyword, exit repeat control
structure, for keyword, forever keyword, next repeat control
structure, until keyword, while keyword, Why does a repeat loop
behave strangely?
Description
Use the repeat control structure to perform the same set of actions
for each member of a set: for example, for each card in a stack, or
each line in a variable.
Form:
The repeat control structure always begins with the word "repeat".
The last line of a repeat control structure is the end repeat keyword.
Parameters:
The loopForm is one of the following forms:
* forever
* until condition
* while condition
* [for] number times
* with counter = startValue [to | down to] endValue [step increment]
* for each chunkType labelVariable in container
* for each element labelVariable in array
The condition is any expression that evaluates to true or false.
The number, startValue, endValue, and increment are numbers or
expressions that evaluate to numbers.
The counter or labelVariable is a legal variable name.
The chunkType is one of character (or char), word, line, item, or token.
The container is any existing container. The array is any existing
container that contains an array of values.
The statementList consists of one or more Transcript statements, and
can also include if, switch, try, or repeat control structures.
Comments:
How many times the statementList is executed depends on the loopForm you use.
The forever form:
The forever form continues repeating the statements in the
statementList until an exit, exit repeat, pass, or return statement
is executed. Usually, one of these control structures is included in
an if control structure within the statementList.
Use the forever form if you want to test a condition at the bottom of
the loop, after the statementList is executed. In the following
example, the go command is executed at least once, since the
mouseClick is not checked until after the go command:
repeat forever
go next card
if the mouseClick then exit repeat -- user clicked
end repeat
If no loopForm is specified, the forever form is used.
The until and while forms:
The until condition and while condition forms repeat the
statementList as long as the condition is false or as long as it is
true, respectively. Revolution re-evaluates the condition before each
iteration.
Use the until condition or while condition form if you want to test a
condition at the top of the loop, before the statements are executed.
This example scrolls through the cards until the user clicks the
mouse:
repeat until the mouseClick
go next
wait for 100 milliseconds
end repeat
The for form:
The for number times form repeats the statementList for the specified
number of times.
The number is evaluated when the loop is first entered, and is not
re-evaluated as a result of any actions performed in the
statementList. For example, if the number is the number of cards, and
the statementList contains a create card command, the loop is
executed as many times as there were cards when the loop began, even
though the current number of cards is changing with each iteration
through the loop.
If the number is not an integer, it is rounded to the nearest
integer, using the same rules as the round function.
Use the for number times form if you want to execute the
statementList a fixed number of times. The following simple example
beeps three times:
repeat for 3 times
beep
end repeat
The with form:
The with counter = startValue to endValue form and the with counter =
startValue down to endValue form set the counter to the startValue at
the beginning of the loop, and increase (or decrease, if you're using
the down to form) the countVariable by 1 each time through the loop.
When the counter is greater than or equal to the endValue, (less than
or equal to, if you're using the down to form), the loop performs its
final iteration and then ends.
If you specify an increment, the increment is added to the counter
each time through the loop, rather than the counter being increased
by 1. (The increment is not treated as an absolute value: if you're
using the down to form, the increment must be negative.)
As with the for number times form described above, the startValue and
endValue are evaluated when the loop is first entered, and are not
re-evaluated as a result of any actions performed in the
statementList.
Use one of these forms if you want to perform an action on each
member of a set, and you need to refer to the member by number within
the statementList. The following example loops through all the
controls on the current card. The counter x is 1 during the first
iteration, 2 during the second, and so on:
repeat with x = 1 to the number of controls
show control x
end repeat
The following example loops backwards through a set of lines. The
counter myLine is 20 during the first iteration, 18 during the
second, and so on:
repeat with myLine = 20 down to 1 step -2
put myLine
end repeat
Note: It is possible to change the counter variable in a statement
in the loop. However, doing this is not recommended, because it makes
the loop logic difficult to follow:
repeat with x = 1 to 20 -- this loop actually repeats ten times
answer x
add 1 to x -- not recommended
end repeat
The for each form:
The for each chunkType labelVariable in container form sets the
labelVariable to the first chunk of the specified chunkType in the
container at the beginning of the loop, then sets it to the next
chunk for each iteration. For example, if the chunkType is word, the
labelVariable is set to the next word in the container for each
iteration of the loop.
Use the for each form if you want to perform an action on each chunk
in a container. This form is much faster than the with countVariable
= startValue to endValue form when looping through the chunks of a
container. The following example changes a return-delimited list to a
comma-delimited list:
repeat for each line thisLine in myList
put thisLine & comma after newList
end repeat
if last char of newList is comma then delete last char of newList
The for each element labelVariable in array form sets the
labelVariable to the first element in the array at the beginning of
the loop, then sets it to the next element for each iteration.
Important! You cannot change the labelVariable in a statement
inside the loop. Doing so will cause a script error. You can change
the content of the container, but doing so will probably produce
unexpected results.
Use the for each form if you want to perform an action on each
element in an array. The following example gets only the multi-word
entries in an array of phrases:
repeat for each element thisIndexTerm in listOfTerms
if the number of words in thisIndexTerm > 1
then put thisIndexTerm & return after multiWordTerms
end repeat
Note: The repeat control structure is implemented internally as a
command and appears in the commandNames.
Changes to Transcript:
The ability to specify an increment for the repeat with counter =
startValue to endValue form was added in version 2.0. In previous
versions, this form of the repeat control structure always
incremented or decremented the counter by 1 each time through the
loop.
--
Michael J. Lew
Senior Lecturer
Department of Pharmacology
The University of Melbourne
Parkville 3010
Victoria
Australia
Phone +613 8344 8304
**
New email address: [EMAIL PROTECTED]
**
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