The code at the bottom of this email displays either a bug
in REBOL 2.3.0.4.2 or a bug in my head. The sample was
quickly cut down from a larger program under development
to try to demonstrate the key issue, so it's a bit untidy.
The code was supposed to perform a sort of 2-d traversal
of the alphabet. After a letter is picked for the row,
pick a letter for the column and, in the original program,
do something which involves comparing the row and column
letters.
In the sample output immediately below, it is obvious that
one method of getting the row letter (using a shared local
variable) fails miserably, getting stuck on the dummy
value to which that variable was initialized, and never
sees any subsequent changes to the variable. The second
method of getting the row letter (passing it as an argument)
works, demonstrating that the letter is actually changing.
A : ~ B : ~ C : ~ D : ~ E : ~ F : ~ G : ~
A : A B : A C : A D : A E : A F : A G : A
A : ~ B : ~ C : ~ D : ~ E : ~ F : ~ G : ~
A : B B : B C : B D : B E : B F : B G : B
A : ~ B : ~ C : ~ D : ~ E : ~ F : ~ G : ~
A : C B : C C : C D : C E : C F : C G : C
A : ~ B : ~ C : ~ D : ~ E : ~ F : ~ G : ~
A : D B : D C : D D : D E : D F : D G : D
A : ~ B : ~ C : ~ D : ~ E : ~ F : ~ G : ~
A : E B : E C : E D : E E : E F : E G : E
A : ~ B : ~ C : ~ D : ~ E : ~ F : ~ G : ~
A : F B : F C : F D : F E : F F : F G : F
A : ~ B : ~ C : ~ D : ~ E : ~ F : ~ G : ~
A : G B : G C : G D : G E : G F : G G : G
So... Why does 'doindx1 fail, while 'doindx2 succeeds?
Shouldn't changes to the local variable 'initial in
'run be visible to both of them (albeit by different
mechanisms)?
-jn-
REBOL []
bug: make object! [
run: function [
][
initial alphabet letter doindx
][
initial: #"~"
letter: #"~"
doindx1: func [] [
foreach letter alphabet [
prin [letter ":" initial " "]
]
print " "
]
doindx2: func [initial] [
foreach letter alphabet [
prin [letter ":" initial " "]
]
print " "
]
alphabet: "ABCDEFG"
foreach initial alphabet [
doindx1
doindx2 initial
print " "
]
]
]
