huddle is a data format for representing an ordered tree in which containers are distinct from values.
Although the two container formats provided Tcl, list and dict, are homoiconic, they don't provide enough information to distinguish a container from a value. Huddle provides a list-based data format in which values are tagged. Each item is a list where the first value is a tag indicating the type of the second value. Use addType add new types.
AK, from Feature request #297 Serialize Helper :
let me try to describe it in my own words. 1. Huddle provides a generic Tcl-based serialization format 2. The entries in that format are tagged with simple type information 3. The currently the known types are 'L' for list, and 'D' for dict ([AMG]: also 's' for string, 'num' for number, 'b' for true/false, and 'null') 4. When converting huddle-notation to other serialization formats like JSON or YAML this type information is used to select the proper notation. 5. And when going from JSON/YAML/... to huddle their notation can be used to select the proper huddle type. 6. In that manner huddle can serve as a common intermediary format. 7. The nice thing about its notation that Tcl can read this format directly (list/dict commands) without the need for a special parser.
# create as a dict
% set bb [huddle create a b c d]
HUDDLE {D {a {s b} c {s d}}}
# create as a list
% set cc [huddle list e f g h]
HUDDLE {L {{s e} {s f} {s g} {s h}}}
% set bbcc [huddle create bb $bb cc $cc]
HUDDLE {D {bb {D {a {s b} c {s d}}} cc {L {{s e} {s f} {s g} {s h}}}}}
% set folding [huddle list $bbcc p [huddle list q r] s]
HUDDLE {L {{D {bb {D {a {s b} c {s d}}} cc {L {{s e} {s f} {s g} {s h}}}}} {s p} {L {{s q} {s r}}} {s s}}}
# normal Tcl's notation
% huddle strip $folding
{bb {a b c d} cc {e f g h}} p {q r} s
# get a sub node
% huddle get $folding 0 bb
HUDDLE {D {a {s b} c {s d}}}
% huddle gets $folding 0 bb
a b c d
# overwrite a node
% huddle set folding 0 bb c kkk
HUDDLE {L {{D {bb {D {a {s b} c {s kkk}}} cc {L {{s e} {s f} {s g} {s h}}}}} {s p} {L {{s q} {s r}}} {s s}}}
# remove a node
% huddle remove $folding 2 1
HUDDLE {L {{D {bb {D {a {s b} c {s kkk}}} cc {L {{s e} {s f} {s g} {s h}}}}} {s p} {L {{s q}}} {s s}}}
% huddle strip $folding
{bb {a b c kkk} cc {e f g h}} p {q r} s
# dump as a JSON stream
% huddle jsondump $folding
[
{
"bb": {
"a": "b",
"c": "kkk"
},
"cc": [
"e",
"f",
"g",
"h"
]
},
"p",
[
"q",
"r"
],
"s"
]Currently, you can get the library at head of tcllib CVS(https://core.tcl-lang.org/tcllib/dir?name=modules/yaml/ ) that is used to implement YAML library.
Lars H: The feature demonstrated in the folding example strikes me as somewhat dangerous; it seems to imply that you cannot store a string that looks like a huddle inside a huddle without having it interpreted as such and fused with the huddle. I suppose it is by design, and an edge case that "won't happen accidentally in real life", but it's a kind of thing that worries me deeply. To protect against it, one would probably have to put all strings in some kind of string container.
kanryu 2008-06-10:
As pointed out, there is a special meaning to the label "HUDDLE" in huddle objects. It need to be careful to store as a child node.
# huddle like string
% set hh {HUDDLE {like string}}
HUDDLE {like string}
# It is not correct
% huddle create p q r $hh
HUDDLE {D {p {s q} r {like string}}}
# It need to wrap the node.
% set ff [huddle wrap s $hh]
HUDDLE {s {HUDDLE {like string}}}
% huddle create p q r $ff
HUDDLE {D {p {s q} r {s {HUDDLE {like string}}}}}About the case of being other, there is no assumption of huddle nodes except for possible handling as a node of Tcl-list. Therefore, not only a simple English words but a multi-byte character, binary data, etc. are storable.
dbohdan 2014-08-02: It's worth pointing out that the yaml package uses its own set of huddle type tags that correspond to a subset those in the YAML spec .
eltclsh > package req yaml
0.3.6
eltclsh > package req huddle
0.1.5
eltclsh > ::yaml::yaml2huddle [::yaml::huddle2yaml {HUDDLE {L {{s a} {D {b {s c}}}}}}]
HUDDLE {!!seq {{!!str a} {!!map {b {!!str c}}}}}
eltclsh > tail -n 13 /usr/share/tcl8.5/tcllib-1.15/yaml/yaml.tcl
huddle addType ::yaml::_huddle_mapping
huddle addType ::yaml::_huddle_sequence
huddle addType [::yaml::_makeChildType string !!str]
huddle addType [::yaml::_makeChildType string !!timestamp]
huddle addType [::yaml::_makeChildType string !!float]
huddle addType [::yaml::_makeChildType string !!int]
huddle addType [::yaml::_makeChildType string !!null]
huddle addType [::yaml::_makeChildType string !!true]
huddle addType [::yaml::_makeChildType string !!false]
huddle addType [::yaml::_makeChildType string !!binary]
huddle addType [::yaml::_makeChildType plain !!plain]I think using those longer tags actually makes the format more readable for humans.