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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, 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  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.

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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