=head1 NAME Slice -- Extract pre-defined slices from an ASCII file =head1 SYNOPSIS B [B<-v>] [B<-o> I:I[@I] ..] [I] B [B<-V>] [B<-h>] =head1 DESCRIPTION =head2 Input Principle The F program reads I (or from F if I is not given or equal ``C<->'') and divides its already prepared ASCII contents into possibly overlapping areas, called I. These slices are determined by enclosing blocks defined by begin and end delimiters which have to be I in the file. These block delimiters use the syntax [NAME: ... :NAME] or alternatively (if there is no misinterpretation possible, i.e. no overlapping or stacked slices) [NAME: ... :] There can be as many such slice definitions as you like and there can be more than one slice with the same name. The resulting slice is the union of all equal named slices. Actually use this to spread a big slice over disjunct peaces of I. =head2 Output Selection Scheme The final output data gets calculated by a slice term consisting of slice names and set theory operators. The following syntax is recognized (in order of LR(1) grammar parsing) for slice terms: =over =item SLICE_TERM ::= C The slice NAME itself. =item SLICE_TERM ::= C | C<~NAME> The B of slice NAME (i.e. ALL\NAME). In formula: {x in ALL: x B in NAME} =item SLICE_TERM ::= C, C The B relation between slice NAME1 and slice NAME2. In set theory also called B: (NAME1uNAME2)\(NAME1nNAME2) or alternatively (NAME1n!NAME2)u(!NAME1nNAME2). In formula: {x in ALL: (x in NAME1 or x in NAME2) and not (x in NAME1 and x in NAME2)}. =item SLICE_TERM ::= C, C The B of slice NAME1 and slice NAME2, i.e. NAME1 minus NAME2. In formula: {x in ALL: x in NAME1 B x B in NAME2} =item SLICE_TERM ::= C | C The B of slice NAME1 and slice NAME2. In formula: {x in ALL: x in NAME1 B x in NAME2} =item SLICE_TERM ::= C, C The B of slice NAME1 and slice NAME2. In formula: {x in ALL: x in NAME1 B x in NAME2} =item SLICE_TERM ::= C<(> SLICE_TERM C<)> A grouped slice term. Use this to force a different order of evaluation. =back =head2 Advanced Selection: Slice Levels Because slices can be overlapping and stacked, a definition level is assigned to each slice while the input is parsed. These levels range from 1 to the maximum encountered (the level 0 is the whole file, i.e. C). When a slice begins, it is assigned the lowest free level, beginning with level 1. As long as one level is in use, it cannot be assigned again until the end delimiter of the corresponding slice is seen. An example: [A:[B::B]:A][C:[D:[E::C]:D][F::E]:F] 3 E-----------E 2 B--B D--------D 1 A--------A C--------C F-----F 0 Here slice A is assigned level 1. Then B is assigned level 2 because level 1 is still in use by A. Then the end of B is reached, level 2 is freed. Then the end of A is reached and level 1 is also free now, so C is assigned level 1 again. Now only level 1 is in use, so D is assigned level 2. Then E is assigned level 3. Then the end of C is seen and level 1 freed. Then the end of D is seen and level 2 is freed. Now F begins and because only level 3 is in use, it gets level 1 assigned. Then the end of E frees level 3 and the end of F frees level 1. Finally no levels are still in use. This indicates that the slicing is correct. If there are any used levels left at the end of this process this indicates an input error and F responds with an error message displaying the still open slices. This complicated level mechanism is needed for granular set operations where particular slices should be included or excluded only. So, to make life easier, a few pseudo-slices are automatically defined: =over =item C The union of all user-defined slices at exactly level n (0 <= n <= oo). =item C The union of all B-user-defined slices at exactly level n (0 <= n <= oo). This actually is just C. =item C The union of all user-defined slices at B levels, beginning at level B<1>. This actually is the union of all C slices. =item C The union of all B-user-defined slices at B levels, beginning with B<1>. This actually is just C. =item C The whole file. This actually is just C, because at level 0 there are no user defined slices, so all is undefined. =item IC<@> This is the slice I minus the union of all C slices with min(NAME) <= n <= oo. Here min(NAME) is the the lowest level plus one where I ever occurred. You can read this as ``NAME without all other slices at higher levels which overwrite it''. B. =back =head1 OPTIONS =over =item [B<-o> I:I[@I] ..] This redirects the output to a file. Usually the whole file will be send to C (same as C). You can use this option I to output to more than one file while the corresponding I determines which output data will be included into each output file. The optional I string is intended for specifying options for the F command, which is applied to I after writing. For instance use ``C'' to make sure the file is readable by a webserver of ``C'' to create a file with the execution bit set (usually used for SSI files on a webserver with the C option available). =item B<-v> This sets verbose mode where some processing information will be given on the console for debugging purpose. =item B<-V> Displays the version identification string. =item B<-h> Displays the usage page. =back =head1 SPECIAL FEATURE Sometimes it can be very useful to be able to provide command line options directly within the input file, for instance to setup one or more B<-o> options. For this F recognizes lines of the form %!slice OPTIONS in the input file and automatically adds OPTIONS to the argument line options. These lines have to start in column 0. Example: %!slice -oTOC:contents.txt =head1 EXAMPLE Assume the following simple multi-language article file F, written in HTML: [EN:Titlepage:][DE:Titelseite:]

[EN:The Title itself:][DE:Der Titel selbst:]

[EN:...English Abstract...:] [DE:...Deutsche Zusammenfassung...:]
[EN:...English Text...:] [DE:...Deutscher Text...:] The command slice -o ENuUNDEF:article.html.en -o DEuUNDEF:article.html.de then creates the following to files: =over =item F: Titlepage

The Title itself

...English Abstract...
...English Text... =item F: Titelseite

Der Titel selbst

...Deutsche Zusammenfassung...
...Deutscher Text... =back =head1 RESTRICTION The current implementation only handles anonymous end delimiters ``C<:]>'' correct in clear cases where no mis-interpretation is possible, i.e. when no overlapping occurs. For instance in ...[A:...[B:...:A]...:]... the end delimiter is not correctly assign to the `B' slice. So, be careful when using anonymous end delimiters in overlapping situations. Pure stacking like ...[A:...[B:...:]...:]... is allowed and handled correctly, but only when you interpret this as ...[A:...[B:...:B]...:A]... =head1 AUTHOR Ralf S. Engelschall rse@engelschall.com www.engelschall.com =cut