Problem with context and property - rebol

Question

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 ?

Answer 1

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...

Answer 2

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