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OpenDarwin 7.2.1 - man page for tcl_exprboolean (opendarwin section 3)

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Tcl_ExprLong(3) 		      Tcl Library Procedures			  Tcl_ExprLong(3)

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NAME
       Tcl_ExprLong, Tcl_ExprDouble, Tcl_ExprBoolean, Tcl_ExprString - evaluate an expression

SYNOPSIS
       #include <tcl.h>

       int
       Tcl_ExprLong(interp, string, longPtr)

       int
       Tcl_ExprDouble(interp, string, doublePtr)

       int
       Tcl_ExprBoolean(interp, string, booleanPtr)

       int
       Tcl_ExprString(interp, string)

ARGUMENTS
       Tcl_Interp   *interp	  (in)	    Interpreter  in  whose  context to evaluate string or
					    objPtr.						  |

       CONST char   *string	  (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 string 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 object-based procedures Tcl_ExprLongObj,  Tcl_ExprDoubleObj,  Tcl_ExprBooleanObj,  and
       Tcl_ExprObj.   Those  object-based  procedures evaluate an expression held in a Tcl object
       instead of a string.  The object 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  trun-
       cated  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.	If the expression's actual value is an integer then Tcl_ExprString converts it to
       a string using sprintf with a ``%d'' converter.	If the expression's  actual  value  is	a
       floating-point  number,	then  Tcl_ExprString  calls  Tcl_PrintDouble  to  convert it to a
       string.

SEE ALSO
       Tcl_ExprLongObj, Tcl_ExprDoubleObj, Tcl_ExprBooleanObj, Tcl_ExprObj

KEYWORDS
       boolean, double, evaluate, expression, integer, object, string

Tcl					       7.0				  Tcl_ExprLong(3)
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