NAME

       Tcl_ExprLong, Tcl_ExprDouble, Tcl_ExprBoolean, Tcl_ExprString - evaluate an expression

SYNOPSIS

       #include <tcl.h>

       int
       Tcl_ExprLong(interp, expr, longPtr)

       int
       Tcl_ExprDouble(interp, expr, doublePtr)

       int
       Tcl_ExprBoolean(interp, expr, booleanPtr)

       int
       Tcl_ExprString(interp, expr)

ARGUMENTS

       Tcl_Interp *interp (in)              Interpreter in whose context to evaluate expr.

       const char *expr (in)                Expression to be evaluated.

       long *longPtr (out)                  Pointer  to  location  in  which  to  store the integer value of the
                                            expression.

       int *doublePtr (out)                 Pointer to location in which to store the  floating-point  value  of
                                            the expression.

       int *booleanPtr (out)                Pointer  to  location in which to store the 0/1 boolean value of the
                                            expression.
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DESCRIPTION

       These four procedures all evaluate the expression given by the expr argument and return the result in one
       of  four  different  forms.  The expression can have any of the forms accepted by the expr command.  Note
       that these  procedures  have  been  largely  replaced  by  the  value-based  procedures  Tcl_ExprLongObj,
       Tcl_ExprDoubleObj,  Tcl_ExprBooleanObj,  and  Tcl_ExprObj.   Those  value-based  procedures  evaluate  an
       expression held in a Tcl value  instead  of  a  string.   The  value  argument  can  retain  an  internal
       representation that is more efficient to execute.

       The  interp  argument  refers  to  an interpreter used to evaluate the expression (e.g. for variables and
       nested Tcl commands) and to return error information.

       For all of these procedures the return value is a standard Tcl result: TCL_OK means  the  expression  was
       successfully  evaluated,  and TCL_ERROR means that an error occurred while evaluating the expression.  If
       TCL_ERROR is returned then the interpreter's result will hold a message  describing  the  error.   If  an
       error occurs while executing a Tcl command embedded in the expression then that error will be returned.

       If  the  expression is successfully evaluated, then its value is returned in one of four forms, depending
       on which procedure is invoked.  Tcl_ExprLong stores an integer value at *longPtr.   If  the  expression's
       actual  value is a floating-point number, then it is truncated to an integer.  If the expression's actual
       value is a non-numeric string then an error is returned.

       Tcl_ExprDouble stores a floating-point value at *doublePtr.  If  the  expression's  actual  value  is  an
       integer,  it  is  converted  to floating-point.  If the expression's actual value is a non-numeric string
       then an error is returned.

       Tcl_ExprBoolean stores a 0/1 integer value at *booleanPtr.   If  the  expression's  actual  value  is  an
       integer or floating-point number, then they store 0 at *booleanPtr if the value was zero and 1 otherwise.
       If the expression's actual value is a non-numeric string then it must be one of the  values  accepted  by
       Tcl_GetBoolean such as “yes” or “no”, or else an error occurs.

       Tcl_ExprString returns the value of the expression as a string stored in the interpreter's result.

SEE ALSO

       Tcl_ExprLongObj, Tcl_ExprDoubleObj, Tcl_ExprBooleanObj, Tcl_ExprObj

KEYWORDS

       boolean, double, evaluate, expression, integer, value, string