--- TODO 2001/11/20 15:33:07 1.6
+++ TODO 2001/12/13 09:20:37 1.7
@@ -62,3 +62,71 @@
Callback Array-Elemente abgefragt.
- Abgabe: 6.12.2001 zum Nikolaustag im CVS.
+
+ **** CLARIFICATION ****
+
+ < [ $HOME ${ARRAY} ]
+ is same as > [ $HOME ${ARRAY[0]} ]
+ must use > [ $HOME ${ARRAY[#]} ]
+
+ Correction to termination condition: we loop unless all ARRAYs containing
+ '#' somewhere in the index expression return undefined. Any array using an
+ constant index and scalar variables are ignored when evaluating the
+ termination condition. Additionally we need support for explicit indexing,
+ ranges and stepping using the following "regex-style" quantifiers:
+
+ [ ... body ... ]{begin,step,end}
+ [ ... body ... ]{begin,end}
+
+ begin, step and end can be digits or arithmetic expressions
+ using variables (exactly like the index expressions) or empty
+ string with default for the empty string
+ - begin = 0
+ - step = 1
+ - end = maximum of all $#{anyvar} where ${anyvar[...#...]}
+ occurs in body.
+
+ {,,} is same as {0,end} and can be omitted.
+
+ < ${ARRAY:s/foo/bar:#}
+ is same as > ${ARRAY[0]:s/foo/bar/:#}
+
+ This means that operation has nothing to do with arrays but works on
+ scalars.
+
+ Correction to index variable from var_cb_t: this is a signed integer and
+ allows negative, zero and positive indexes. It's up to the lookup callback
+ to decide what is undefined. Some callbacks may support negative indices
+ to support indexing from the end backwards through the array.
+
+ This means negative numbers can not be used as the magic identifier for
+ "gimme the number of elements for this variable".
+
+ The callback needs another input, enum { VAR_LOOKUP_VALUE,
+ VAR_LOOKUP_ELEMENTS, ... } var_lookup_t which tells the callback what to
+ look up. Initially, only these modes are supported but we have room for
+ future expansion here.
+
+ The syntax change to adopt these changes is: $#{foo} returns the number of
+ elements in foo while ${foo:#} returns the number of characters in the
+ expanded value of foo. This keeps :# an command and makes ${foo} executing
+ callback with VAR_LOOKUP_VALUE and $#{foo} executing callback with
+ VAR_LOOKUP_ELEMENTS. Additionally it adopts Perl syntax. Extreme case:
+ $#{foo:#} tells you how many digits the number of elements of foo has.
+
+ Examples now working correctly:
+
+ - Creation of a Newsgroups: header from To: headers w/o the last comma
+
+ Newsgroup: [${To[#]}${To[#+1]:+${Separator} }]
+ Newsgroup: [${To[#-1]:+${Separator} }${To[#]}]
+
+ - Assume index zero is a header and the last element is a footer. Print a
+ table with header, ruler, body, ruler and footer.
+
+ ${foo[0]}
+ ${empty:p/-/${foo[0]:#}/}
+ [$foo{#}\n]{1,$#{foo}-1}
+ ${empty:p/-/${foo[$#{foo}]:#}/}
+ ${foo[$#{foo}]}
+
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