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Practical Programming in Tcl & Tk, Third Edition by Brent B. Welch

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A C Command Procedure

Tcl 8.0 introduced a new interface for Tcl commands that is designed to work efficiently with its internal on-the-fly byte code compiler. The original interface to commands was string oriented. This resulted in a lot of conversions between strings and internal formats such as integers, double-precision floating point numbers, and lists. The new interface is based on the Tcl_Obj type that can store different types of values. Conversions between strings and other types are done in a lazy fashion, and the saved conversions help your scripts run more efficiently.

This section shows how to build a random number command using both interfaces. The string-based interface is simpler, and we start with that to illustrate the basic ...

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