[REBOL] Re: [context] How to compose in a local context
From: Gary:Jones:usap:gov at: 22-Apr-2004 9:38
From: Ashley Tr=FCter
Given the following:
>> b: 'a
== a
>> do has [a][set 'a 0]
== 0
>> a
** Script Error: a has no value
** Near: a
>> do has [a][do compose/deep [set [(b)] 0]]
== 0
>> a
== 0
How can I prevent 'compose from binding to the global context?
****
Hi, Ashley,
I'm not an expert on binding, but as you seem to be aware, it appears as though the order
of evaluation has 'a being set to 0 in the global context by way of the 'do command *inside*
the block. An alternative approach is to "compose" the full line:
b: 'a
do compose/deep [has [a][set (to-lit-word b) 0]]
The actual lines I used in order to be sure that I had it right was:
b: 'a
do compose/deep [
c: has [a][
set (to-lit-word b) 0
print (b)
]
]
such that:
>> do compose/deep [
[ c: has [a][
[ set (to-lit-word b) 0
[ print (b)
[ ]
[ ]
>> c
0
>> a
** Script Error: a has no value
** Near: a
>> b
== a
>>
Finally, if you want to get the function ready but not run it, then:
b: 'a
reduce compose/deep [
c: has [a][
set (to-lit-word b) 0
print (b)
]
]
Hope that helps.
--Scott Jones
