Rebol has apply Creating map function in Red language what's the equivalent of Rebol apply in Red if any ?
Currently, there's no native apply in Red. You can write apply on your own:
apply: func [
"Apply a function to a block of arguments"
fn [any-function!] "Function value to apply"
args [block!] "Block of arguments (to quote refinement use QUOTE keyword)"
/local refs vals val
][
refs: copy []
vals: copy []
set-val: [set val skip (append/only vals val)]
parse args [
some [
'quote set-val
| set val refinement! (append refs to word! val)
| set-val
]
]
do compose [(make path! head insert refs 'fn) (vals)]
]
It works bit differently than Rebol's apply (because I don't like Rebol's apply syntax). If you define some function:
f: func [
foo
/bar
baz
][
reduce [foo bar baz]
]
then here's how to use this apply:
>> apply :f [1 /bar 1]
== [1 true 1]
>> apply :f [quote /bar]
== [/bar false none]
>> apply :f [quote /bar /bar 1]
== [/bar true 1]
See http://red.qyz.cz/apply-and-ufcs.html for details.
Related
When I call f without parameter, I got the error Script Error: if does not allow unset! for its then-blk argument why ?
f: func['p [string! unset!]][
if unset? 'p print "unset"
]
'p evaluates to the word p. In order to test the type of the value referred by p, you need to use :p and provide a proper body block for if:
f: func ['p [string! unset!]][
if unset? :p [print "unset"]
]
>> f "123"
== none
>> f
unset
Let's say I want to generate this output:
public String toString() {
return this.getFirstName() + "," + this.getLastName() + "," + this.getAge();
}
from the template below and a custom recursive build-markup function:
template-toString: {this.get<%property%>() <%either not context.build-markup/EOB [{+ "," +}][""]%> }
build-markup/vars template-toString [property] ["FirstName" "LastName" "Age"]
My problem is to avoid the last element to be concatenate with {+ "," +}
My idea was to use a context.build-markup with an EOB property (End Of Block) that would be set to true when last element is processed. Then I could use in template-toString above either not context.build-markup/EOB [{+ "," +}][""] to concatenate or not with {+ "," +} :
context.build-markup: context [
EOB: false
set 'build-markup func [
{Return markup text replacing <%tags%> with their evaluated results.}
content [string! file! url!]
/vars block-fields block-values
/quiet "Do not show errors in the output."
/local out eval value n max i
][
out: make string! 126
either not vars [
content: either string? content [copy content] [read content]
eval: func [val /local tmp] [
either error? set/any 'tmp try [do val] [
if not quiet [
tmp: disarm :tmp
append out reform ["***ERROR" tmp/id "in:" val]
]
] [
if not unset? get/any 'tmp [append out :tmp]
]
]
parse/all content [
any [
end break
| "<%" [copy value to "%>" 2 skip | copy value to end] (eval value)
| copy value [to "<%" | to end] (append out value)
]
]
][
n: length? block-fields
self/EOB: false
actions: copy []
repeat i n [
append actions compose/only [
;set in self 'EOB (i = n)
set in system/words (to-lit-word pick (block-fields) (i)) get pick (block-fields) (i)
]
]
append actions compose/only [
append out build-markup content
]
foreach :block-fields block-values actions
if any [(back tail out) = "^/" (back tail out) = " " (back tail out) = "," (back tail out) = ";" (back tail out) = "/" (back tail out) = "\"] [
remove back tail out
]
]
out
]
]
But my attempt failed (so I commented ;set in self 'EOB (i = n) because it doesn't work). How to correct the code to get what I want ?
I'm quite certain you could be achieving your goal in a cleaner way than this. Regardless, I can tell you why what you're doing isn't working!
Your n is the expression length? block-fields, and your repeat loop goes up to n. But block-fields contains the single parameter [property]! Hence, it loops from 1 to 1.
You presumably wanted to test against something enumerating over block-values (in this example a range from 1 to 3) and then handle it uniquely if the index reached 3. In other words, your set in self 'EOB expression needs to be part of your enumeration over block-values and NOT block-fields.
This would have given you the behavior you wanted:
n: length? block-values
i: 1
foreach :block-fields block-values compose/only [
set in self 'EOB equal? i n
do (actions)
++ i
]
This absolutely won't work:
append actions compose/only [
set in self 'EOB (i = n)
set in system/words (to-lit-word pick (block-fields) (i)) get pick (block-fields) (i)
]
...because you are dealing with a situation where i and n are both 1, for a single iteration of this loop. Which means (i = n) is true. So the meta-code you get for "actions" is this:
[
set in self 'EOB true
set in system/words 'property get pick [property] 1
]
Next you run the code with a superfluous composition (because there are no PAREN!s, you could just omit COMPOSE/ONLY):
append actions compose/only [
append out build-markup content
]
Which adds a line to your actions meta-code, obviously:
[
set in self 'EOB true
set in system/words 'property get pick [property] 1
append out build-markup content
]
As per usual I'll suggest you learn to use PROBE and PRINT to look and check your expectations at each phase. Rebol is good about dumping variables and such...
You seem to making something simple very complicated:
>> a: make object! [
[ b: false
[ set 'c func[i n] [b: i = n]
[ ]
>> a/b
== false
>> c 1 4
== false
>> a/b
== false
>> c 1 1
== true
>> a/b
== true
... and I'm hitting the wall, I don't understand why this doesn't work (I need to be able to parse either the single tag version (terminated with />) or the 2 tag versions (terminated with ) ):
Rebol[]
content: {<pre:myTag attr1="helloworld" attr2="hello"/>
<pre:myTag attr1="helloworld" attr2="hello">
</pre:myTag>
<pre:myTag attr3="helloworld" attr4="hello"/>
}
spacer: charset reduce [#" " newline]
letter: charset reduce ["ABCDEFGHIJKLMNOPQRSTUabcdefghijklmnopqrstuvwxyz1234567890="]
rule: [
any [
{<pre:myTag}
any [any letter {"} any letter {"}] mark:
(print {clipboard... after any letter {"} any letter {"}} write clipboard:// mark input)
any spacer mark: (print "clipboard..." write clipboard:// mark input) ["/>" | ">"
any spacer </pre:myTag>
]
any spacer
(insert mark { Visible="false"})
]
to end
]
parse content rule
write clipboard:// content
print "The end"
input
In this case, the problem isn't your rule - it's that your 'insert after each tag changes alters the position at the point you do the insert.
To illustrate:
>> probe parse str: "abd" ["ab" mark: (insert mark "c") "d"] probe str
false
"abcd"
== "abcd"
The insert is correct, but after the insert, the parse rule is still at position 2, and before where there was just "d", there is now "cd" and the rule fails. Three strategies:
1) Incorporate the new content:
>> probe parse str: "abd" ["ab" mark: (insert mark "c") "cd"] probe str
true
"abcd"
== "abcd"
2) Calculate the length of the new content and skip:
>> probe parse str: "abd" ["ab" mark: (insert mark "c") 1 skip "d"] probe str
true
"abcd"
== "abcd"
3) Change the position after the manipulation:
>> probe parse str: "abd" ["ab" mark: (mark: insert mark "c") :mark "d"] probe str
true
"abcd"
== "abcd"
Number 2) would be the quickest in your case as you know your string length is 16:
rule: [
any [
{<pre:myTag} ; opens tag
any [ ; eats through all attributes
any letter {"} any letter {"}
]
mark: ( ; mark after the last attribute, pause (input)
print {clipboard... after any letter {"} any letter {"}}
write clipboard:// mark
input
)
any spacer mark: ; space, mark, print, pause
(print "clipboard..." write clipboard:// mark input)
[ ; close tag
"/>"
|
">" any spacer </pre:myTag>
]
any spacer ; redundant without /all
(insert mark { Visible="false"})
16 skip ; adjust position based on the new content
]
to end
]
Note: this is the same rule as yours with just [16 skip] added.
It is possible to overide rebol system words like print, make etc., so is it possible to do the same with the path operator ? Then what's the syntax ?
Another possible approach is to use REBOL meta-programming capabilities and preprocess your own code to catch path accesses and add your handler code. Here's an example :
apply-my-rule: func [spec [block!] /local value][
print [
"-- path access --" newline
"object:" mold spec/1 newline
"member:" mold spec/2 newline
"value:" mold set/any 'value get in get spec/1 spec/2 newline
"--"
]
:value
]
my-do: func [code [block!] /local rule pos][
parse code rule: [
any [
pos: path! (
pos: either object? get pos/1/1 [
change/part pos reduce ['apply-my-rule to-block pos/1] 1
][
next pos
]
) :pos
| into rule ;-- dive into nested blocks
| skip ;-- skip every other values
]
]
do code
]
;-- example usage --
obj: make object! [
a: 5
]
my-do [
print mold obj/a
]
This will give you :
-- path access --
object: obj
member: a
value: 5
--
5
Another (slower but more flexible) approach could also be to pass your code in string mode to the preprocessor allowing freeing yourself from any REBOL specific syntax rule like in :
my-alternative-do {
print mold obj..a
}
The preprocessor code would then spot all .. places and change the code to properly insert calls to 'apply-my-rule, and would in the end, run the code with :
do load code
There's no real limits on how far you can process and change your whole code at runtime (the so-called "block mode" of the first example being the most efficient way).
You mean replace (say)....
print mold system/options
with (say)....
print mold system..options
....where I've replaced REBOL's forward slash with dot dot syntax?
Short answer: no. Some things are hardwired into the parser.
Is there a way to do so including creating an other build-markup function ?
Sadly,build-markup uses only global variables: link text says: Note that variables used within tags are always global variables.
Here's a slightly cranky way of doing it using an inner object (bm-1 demonstrates the problem: a and b are printed with their global values; bm-2 is the cranky work around):
a: "global-a"
b: "global-b"
bm-1: func [a b][
print build-markup "<%a%> <%b%>"
]
bm-2: func [a b][
cont: context [
v-a: a
v-b: b
]
print build-markup "<%cont/v-a%> <%cont/v-b%>"
]
bm-1 "aaa" "bbb"
bm-2 "aaa" "bbb"
REBOL3 has reword rather than build-markup. That is much more flexible.
I've patched the build-markup function to be able to use local contexts:
build-markup: func [
{Return markup text replacing <%tags%> with their evaluated results.}
content [string! file! url!]
/bind obj [object!] "Object to bind" ;ability to run in a local context
/quiet "Do not show errors in the output."
/local out eval value
][
content: either string? content [copy content] [read content]
out: make string! 126
eval: func [val /local tmp] [
either error? set/any 'tmp try [either bind [do system/words/bind load val obj] [do val]] [
if not quiet [
tmp: disarm :tmp
append out reform ["***ERROR" tmp/id "in:" val]
]
] [
if not unset? get/any 'tmp [append out :tmp]
]
]
parse/all content [
any [
end break
| "<%" [copy value to "%>" 2 skip | copy value to end] (eval value)
| copy value [to "<%" | to end] (append out value)
]
]
out
]
Here are some example usages:
>> x: 1 ;global
>> context [x: 2 print build-markup/bind "a <%x%> b" self]
"a 2 b"
>> print build-markup/bind "a <%x%> b" context [x: 2]
"a 2 b"