A TCL extension API for C++11

Typesafe C++ Extensions

A small, type-safe, API is provided for writing c++ extensions is provided.

Before invoking a function, the API will:

• Check all arguments have been provided
• Construct the arguments into c++ types (string, int, long and double supported by default)
• Raise a standard error message if an incorrect type has been provided

Also provided by the API:

• Return results by providing the native type
• Throw standard TCL errors within
• Simple to add more supported types

Simple Example

int Repeat(TCL_Interpreter& interp, string phrase, int times) {
    stringstream result;

    for ( int i =0; i< times; i++ ) {
        result << phrase << endl;
    }

    interp.SetResult(result.str());
    return TCL_OK;
}

extern "C"
{
    // Standard TCL hook for pkg_mkIndex
    int Tcltest_Init(Tcl_Interp* theInterpreter) {
       TCL_Interpreter interp(theInterpreter);
       
       // Register the function with the API
       interp.AddCommand("Repeat",Repeat);
       
       // Declare the package we're providing
       return interp.PackageProvide("Tcltest");
    }
}

>>> package require Tcltest
>>> Repeat "Hello World!" 4

Hello World!
Hello World!
Hello World!
Hello World!

Argument Checking

Standard TCL errors are raised for missing or incorrect arguments

>>> Repeat "Hello World!" three

expected integer but got "three"
    while executing
"Repeat "Hello World!" three"
    (file "./pluginTest.tcl" line 177)

Raising custom errors

Lets amend the command with some boundrary case testing

int Repeat(TCL_Interpreter& interp, string phrase, int times) {
    stringstream result;
    
    if ( times < 0 ) {
        interp.RaiseError("repeat must be a positive number!");
    }

    for ( int i =0; i< times; i++ ) {
        result << phrase << endl;
    }

    interp.SetResult(result.str());
    return TCL_OK;
}

>>> Repeat "Hello World!" -1

repeat must be a positive number!
    while executing
"Repeat "Hello World" -1"
    (file "./pluginTest.tcl" line 177)

Readline Integration

An example plugin which integrates with the readline library will be provided...