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Pd release 0.23 and onward include objects for managing lists of data. The
objects allow you to describe data structures and how they are viewed
("template objects") and to traverse lists ("traversal objects.")
The rest of this file gives a highly condensed summary of what's there; the
patches, starting with "1.scalars.pd", act as a tutorial.
1. TEMPLATE OBJECTS.
templates describe data structures. You can add an item to a data structure
using "field" or ask for a shape to be drawn using a "display command."
1.1. "template" -- data structure.
usage, "template <field1> <field2> ..."
where the fields are either "float <name>", "symbol <name>", "list <name>"
(don't try that yet); or "array <name> <template-for-elements>.
1.2. DISPLAY COMMANDS.
These are objects which ask Pd to draw a shape corresponding to some fields
of the datum.
1.2.1. POLYGONS and CURVES.
polygons: polygon <outline-color> <line-width> <x, y> ...
filled polygons: fpolygon <fill-color> <outline-color> <line-width> <x, y> ...
curves: curve <outline-color> <line-width> <x, y> ...
filled curves: fcurve <fill-color> <outline-color> <line-width> <x, y> ...
Each argument can either be a number or a symbol. If a symbol, it's the
name of a field (which must be a "float) which specifies the vaiue.
So for instance in the "1.scalar.pd" example, in the template "template1",
the object "fpolygon 244 q 5 0 0 20 z 40 0" draws a filled polygon whose
interior color is 244 (red 2, green 4, blue 4) but whose outline color
depends on the value of the field "q". Its coordinates describe a triangle
whose altitude is given by "z."
1.2.2 PLOT.
The "plot" objects plots an array field as shown in 5_array.pd.
2. TRAVERSAL.
In this release of Pd, you can only traverse lists all of whose elements
belong to the same template; this restriction will be relaxed in a future
release. You "traverse" a list either to build it, to get its elements,
or to change their values.
2.1. POINTER.
The "pointer" object can be used to refer to an element of a list. Its
methods are:
2.1.1. traverse <symbol>.
Point to the "head" of a list. The symbol should match the name of a Pd
window holding the list. The pointer is output, but you can't set or get the
fields of the "head" pointer; you can only get the "next" element or "append"
to the list.
2.1.2. next. Goes to the next element of the list. Either the pointer
is output on the left side, or else a "bang" at right tells you that no
more objects are forthcoming.
2.1.3. bang.
outputs the current pointer.
2.2. APPEND. Adds an element of the specified template to the list. You
specify what fields you want to supply and the last inlet takes a pointer to
the element you want to "append" after.
2.3. GET.
get <template> <field...>
send it a pointer to an object belonging to the <template> and it outputs
the (floating-point) fields.
2.4. SET.
set <template> <field...>
send it a pointer (at the rightmost inlet) and values for the specified
fields, and their values are changed accordingly.
2.5. GETSIZE.
getsize <template> <array-field>
outputs the size of the named field, which must be an array, when it receives
a pointer to the owner as input.
2.6. SETSIZE.
setsize <template> <array-field>
Send it a pointer to the owner (right inlet) and then the desired size
(left inlet) and the array is resized. If a template contains an array,
each scalar belonging to the template can have its own size for the array.
2.7. ELEMENT.
element <template> <array-field>
Pass it an index and a pointer and it outputs a pointer to an element of the
array.
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