Repend - Function Summary
Summary:
Appends a reduced value to a series and returns the series head.
Usage:
repend series value
Arguments:
series - The series argument. (must be: series port)
value - The value argument.
Refinements:
/only - Appends a block value as a block
Description:
REPEND stands for REDUCE APPEND. It performs the same operation
as APPEND (inserting elements at the tail of a series) but
REDUCES the block of inserted elements first. Just like APPEND,
REPEND returns the head of the series.
For example, writing:
numbers: [1 2 3]
probe repend numbers [2 + 2 2 + 3 3 + 3]
[1 2 3 4 5 6] |
is the same as writing:
numbers: [1 2 3]
probe append numbers reduce [2 + 2 2 + 3 3 + 3]
[1 2 3 4 5 6] |
REPEND is very useful when you want to add to a series elements
that need to be evaluated first. The example below creates a
list of all the .r files in the current directory, along with
their sizes and modification dates.
data: copy []
foreach file load %. [
if %.r = suffix? file [
repend data [file size? file modified? file]
]
]
probe data
[%dictionary.r 7754 5-Jan-2003/11:29:48-8:00 %comments.r 2966 24-Ja
n-2003/22:53:58-8:00 %undoced.r 3172 26-Jan-2003/0:08:16-8:00 %rebol-tes
t-file.r 103 9-Mar-2004/1:00-8:00 %date.r 23 9-Mar-2004/0:58:24-8:00 %da
ta.r 29 9-Mar-2004/0:58:24-8:00 %upload.r 746 9-Mar-2004/0:41:48-8:00 %d
atecode.r 23 9-Mar-2004/0:39:34-8:00 %words.r 185013 9-Mar-2004/0:41:52-
8:00 %dict-html.r 15043 9-Mar-2004/0:59:26-8:00] |
When used with strings, repend is a useful way to join values.
The example below is a common method of generating HTML web
page code:
html: copy "<HTML><BODY>"
repend html [
"Date is: " now/date <P>
"Time is: " now/time <P>
"Zone is: " now/zone <P>
</BODY></HTML>
]
print html
<HTML><BODY>Date is: 9-Mar-2004<P>Time is: 0:59:58<P>Zone is: -8:00
<P></BODY></HTML> |
Related:
append - Appends a value to the tail of a series and returns the series head.
insert - Inserts a value into a series and returns the series after the insert.
join - Concatenates values.
reduce - Evaluates an expression or block expressions and returns the result.
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