| Re: Parsing text files with standard words |
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Group: comp.lang.forth · Group Profile
Author: Josh GramsJosh Grams Date: Sep 15, 2008 18:13
Gerry wrote:
>I think that EXECUTE-PARSING-FILE provides a partial solution...
>
>The reason I say it is a partial solution is because you have to
>define a word to parse and process the file, if another file is
>to be processed by nesting, that word may have to be called again
>so it may need to be re-entrant.
But...if you want to process a nested file, wouldn't the code need
to be re-entrant even if you were using FILE-SOURCE/CLOSE-SOURCE?
>Also it precludes a design where an application opens a file
>source and then returns to whatever called it to parse and
>process the file.
I'll agree with you there, but I don't think that's an option in
many systems anyway; see below.
>Suppose the system is in interpret mode and the user types in
>S" filename" FILE-SOURCE. Having executed FILE-SOURCE, control
>returns to the text interpreter which could simply use the stream
>attached to the new input source.
>
>
>
>When the file source reached the end or CLOSE-SOURCE was
>executed, the system would return to the original input source.
>In this simple example it would therefore behave much like
>INCLUDE-FILE. Are there any conceptual problems with this?
The problem I see is that it requires a separate stack for input
sources. In some systems, EVALUATE/INCLUDE/etc. save the old
input source specification by pushing it onto the rstack, in which
case there is no way for any other word to find and restore it.
Or am I missing something?
--Josh
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