Re: 'withfile' function implementation

[Paul Smith]

On Mon, 2012-01-16 at 13:26 +0000, Tim Murphy wrote:
> There might be some question about how the variable "$(FILE)" would
> look if you tried to iterate over its contents. e.g. would one see an
> iteration for each word and with "\n"s  marking lines or is each line
> an "atom" for want of a better word.

It would work the same way as if you had done:

        define FILE
        this is the first line
        this is the second line
        this is the third line
        endef

        $(foreach W,$(FILE),$(info $W))

In other words, every whitespace-separated token is a word.  Newlines
are just another form of whitespace, to make functions.

There is no way to operate on "lines" in this model.  I suppose, if this
is something people really want, we could make the input mode fancier.
For example, we could say that $(file < input) would read the entire
"input" file and expand to its contents as I mentioned before.

On the other hand $(file << input) would read a single line from the
file "input"; every time it was invoked with the same filename it would
read the next line from that file.  This gets very complicated of
course: how do you know when you're done?  Just returning the empty
string isn't good enough since you'd stop on the first blank line.
Unless you preserved the newline, which is gross... basically you'd need
to $(strip ...) every returned value before using it.  Can you have
multiple input files open at the same time, or will reading from a
different filename automatically close the previous read?  If you can
have multiple input files open do you need a way to "abort" a read
operation?  Etc.

Line-by-line reading is really problematic.  I'm not sure I want to get
into that.

-- 
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