2012-01-31

parsing unmatching opening characters

1.5: adda/parse/algorithm for parsing containers:
. there can be non-matching container parts,
because they can be surounded by complete containers,
eg, ( ... [ ...{} ),
. the recursive way is this:
find an opening to some container,
and then call the function that reads that container;
what else that function will need, though,
is knowing whether it was sent by
another container-reading function;
so, in the example above, ( ... [ ...{} ),
getParen is calling getBracket( ")" ),
so then getBracket knows it needs to be stopping for
both {")", "]"}, whichever come first .
. if getBracket returns nil,
then getParen will know that the "[" should be taken as
a character, not the beginning of a subtree .
. any 3rd possibility?
no, but  it does involve recursive backtracking,
with multiple readers on a single stream: [1.31:
. both caller and called could
fail to find their closing match .
. then to not have to do work over again,
it should have some way remembering
whether a given opening character has a match .
. another needed dimension is being fault tolerant:
if the coder forgot a closing character,
then there should be other ways of parsing
that will be able to guess something is missing;
eg, a line has found an new function definition
in the middle of a function body,
it could guess that the body above is
missing a closing character .]