What: scrobj - scripted Tcl_Objects
Where: http://nullhomotopie.de/programs/scrobj-page.html Description: a Tcl extension that allows you to implement new Tcl_Object types from the script level. Updated: 12/2008 Version: 1.0
Quote from the man page:
Tcl's fundamental mantra says that "everything is a string" and much of
Tcl's simplicity derives from this rule. Strings can, however, carry
with them an internal representation as some other data type, and this
is one reason for Tcl's astonishing performance. For example, Tcl
maintains such an internal representation for integers, lists, byte-
codes, and many other types.
Extension writers have long been able to add new custom types using
Tcl's C interface. The scrobj package allows you to do the same from
the script level.
Unfortunately, in order to achieve this the package has to violate a
basic assumption of Tcl's bytecode engine, namely that it is not get-
ting invoked recursively from a call to Tcl_GetString. A consequence
is that scrobj can be used to crash the application, although this does
require a rather contrived setup.
To prevent such crashes in the legitimate cases the package uses a ded-
icated Tcl interpreter for every registered type. Both Tcl 8.5 and Tcl
8.6 seem to tolerate recursive invocations of the bytecode engine, as
long as they execute in different interpreters.The package also contains two sample applications that implement a little "expr" command for arithmetic with rational numbers.
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