AS_VAR_APPEND [was: [PATCH] Support a stack of LINENO values for AS_MESSAGE.]

[Eric Blake]

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According to Paolo Bonzini on 10/16/2008 1:41 AM:
>> or maybe even write AS_APPEND([var],[text]), which expands to a shell 
>> function 
>> that uses += on bash and traditional appends elsewhere?
> 
> That could be added (but AS_VAR_APPEND please, for consistency).

In addition to appending, we also need to choose the right name for
basename and dirname.

Right now, we have AS_SET_CATFILE, which requires var to be a shell name,
then we have the AS_VAR_* namespace, which is polymorphic to act on both
shell names (literals) and shell indirections.

So, I guess the naming depends on whether we want to support indirections.
 If we name it AS_VAR_APPEND (likewise for AS_VAR_BASENAME), then we use
AS_LITERAL_IF to provide appropriate eval's to dereference indirection
when needed; if we name it AS_SET_APPEND, then the user must pass a
literal name and cannot benefit from indirection.

I think this discussion has convinced me - AS_VAR_APPEND sounds like the
right name, but it means we have to do more work to make it work on both
literals and indirection.

>> And the quadratic nature of this algorithm is only apparent on 
>> heavily nested code; how deep do you anticipate a typical nesting of the 
>> as_lineno_stack to reach?
> 
> Anyway I don't expect more than 5.

Good - all my worries about quadratic behavior are rendered irrelevant, as
optimizing this won't really help performance.

- --
Don't work too hard, make some time for fun as well!

Eric Blake             address@hidden
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