The manual for this [Tcl C API] function is at [http://www.tcl.tk/man/tcl8.5/TclLib/ExprLongObj.htm].
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**Usage example**

A simple Tcl code snippet to produce a random integer from 0 to 255 is:
 return [expr {int(rand()*(255+1))}]

The C function Tcl_ExprLongObj can be used to code this in C like this (assuming this is called from a Tcl interpreter 'interp'):
 Tcl_Obj *exprPtr;   /* pointer to hold the expression we want to evaluate */
 long myresult;      /* the integer holding the result of the expression */
 
 exprPtr = Tcl_NewStringObj("int(rand()*255+1)",-1); /* this prepares the expression, which must be given as a Tcl_Obj */
 /* now evaluate the expression in exprPtr and put the result into myresult */
 if (Tcl_ExprLongObj(interp,exprPtr,&myresult) != TCL_OK) {
     return TCL_ERROR;
 }

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'''[DGP]''' Perhaps worth noting that because Tcl_ExprLongObj() writes
its result to a variable of type 'long', it implicitly performs
the 'int(.)' function as part of its nature.  There's no need to
include the 'int(.)' call in the expression string.

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Similar functions are [Tcl_ExprDoubleObj], [Tcl_ExprBooleanObj], and [Tcl_ExprObj].
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%| Category Tcl library |%
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