Re: Help With Homework: HTML Tables to CALS

Dear XSL-list,

Is there information anywhere about how to construct a memo function? I see
that support for it it is built into Saxon PE and EE, but does anyone know
of an example or description of how to construct a memo function in HE, or
a different XSLT engine that does already incorporate hooks for that
functionality?

Thanks,

David

On Thu, Jan 23, 2020 at 11:15 AM Michael Kay mike@xxxxxxxxxxxx <
xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:

> One technique I have found useful in converting algorithms designed for
> procedural programming languages is to use memo functions. For example, if
> you need to assign  (row, column, height, depth) properties to every cell
> in a table, you don't necessarily need to construct a data structure
> holding that information; if you have a function (or set of functions) that
> computes the properties in terms of the corresponding properties for other
> cells in the table, and if you make that computation a memo function, then
> the data structure is there in the implicit memory of the memo function,
> and doesn't need to be exposed explicitly in variables. To take an example
> with a one-dimensional table where every cell has a colspan attribute, we
> can compute
>
> function f:column($cell) { $cell ! (if (preceding-sibling::cell) then
> (column(preceding-sibling::cell) + (@colspan, 1)[1]) else 1) }
>
> and if this is a memo function, we don't need to worry about the cost of
> repeated computation of the function.
>
> Michael Kay
> Saxonica
>
> On 23 Jan 2020, at 15:59, Eliot Kimber ekimber@xxxxxxxxxxxx <
> xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Andrew's code will almost certainly allow me to solve my immediate problem.
>
> I would still be interested in an XSLT 3 solution that uses arrays or
> maps, but I might be able to work it out myself, although I know that I
> don't fully grok the best/most compact way to do things, for example,
> taking advantage of higher-order functions or fold-* approaches.
>
> Cheers,
>
> E.
> --
> Eliot Kimber
> http://contrext.com
>
>
> o;?On 1/23/20, 9:37 AM, "Martin Honnen martin.honnen@xxxxxx" <
> xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:
>
>    Am 23.01.2020 um 16:30 schrieb Eliot Kimber ekimber@xxxxxxxxxxxx:
>
> I have XSLT 1-style code that converts HTML tables to CALS tables. I
> discovered that this code fails for certain patterns of HTML tables in that
> it miscalculates column spans in the face of row spans earlier in the
> table. It doesn't fail for all tables, just specific ones (which is why we
> didn't notice this bug earlier). I haven't been able to determine the cause
> of the bug in the short time I've had to debug it (found the bug in the
> course of trying to prepare a rush publishing job that has about 50 complex
> tables in it, of course).
>
> Rather than try to debug and fix the XSLT 1 solution it seemed easier and
> better to re-implement the processing using XSLT 3 and I took a stab at
> doing it using arrays last night, but quickly got bogged down in my own
> lack of facility with such things. The procedural solution in i.e., Java,
> would be easy: just populate the 2x2 matrix that represents the table grid
> to reflect row and column spans as you process the table cells
> left-to-right and top to bottom, using cells projected from earlier rows to
> determine the starting column of cells in subsequent rows that get pushed
> over by row-spanning cells.
>
> However, I couldn't quickly see how to do this using arrays or maps in
> XSLT 3--the immutability of arrays and thus the coding patterns that take
> existing arrays or maps and return new ones threw me and my feeble brain
> just wasn't landing on the right algorithmic pattern.
>
> I know there must be a general pattern for this type of processing but
> none of the examples I could find were helpful.
>
> So my request: can someone help me with this challenge and outline how to
> solve this kind of problem where you take as input an HTML table where any
> cell may span two or more columns and two or more rows and produce a 2x2
> array representing the table's grid, where every grid cell reflects the
> HTML table cell that covers it.
>
> From that array it's then easy to determine what the CALS result should be
> (where CALS represents column spans by naming the start and end columns the
> cell spans).
>
>
>    Does Andrew's XSLT 2 code help?
>    http://andrewjwelch.com/code/xslt/table/table-normalization.html
>
>
>
>
>
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