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'\"
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'\" Copyright (c) 1996-1997 Sun Microsystems, Inc.
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'\"
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'\" See the file "license.terms" for information on usage and redistribution
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'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
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'\"
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'\" RCS: @(#) $Id: ExprLongObj.3,v 1.1.1.1 2002-01-16 10:25:23 markom Exp $
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'\"
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.so man.macros
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.TH Tcl_ExprLongObj 3 8.0 Tcl "Tcl Library Procedures"
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.BS
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.SH NAME
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Tcl_ExprLongObj, Tcl_ExprDoubleObj, Tcl_ExprBooleanObj, Tcl_ExprObj \- evaluate an expression
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.SH SYNOPSIS
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.nf
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\fB#include \fR
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.sp
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int
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\fBTcl_ExprLongObj\fR(\fIinterp, objPtr, longPtr\fR)
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.sp
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int
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\fBTcl_ExprDoubleObj\fR(\fIinterp, objPtr, doublePtr\fR)
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.sp
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int
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\fBTcl_ExprBooleanObj\fR(\fIinterp, objPtr, booleanPtr\fR)
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.sp
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int
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\fBTcl_ExprObj\fR(\fIinterp, objPtr, resultPtrPtr\fR)
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.SH ARGUMENTS
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.AS Tcl_Interp *resultPtrPtr out
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.AP Tcl_Interp *interp in
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Interpreter in whose context to evaluate \fIstring\fR or \fIobjPtr\fR.
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.AP Tcl_Obj *objPtr in
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Pointer to an object containing the expression to evaluate.
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.AP long *longPtr out
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Pointer to location in which to store the integer value of the
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expression.
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.AP int *doublePtr out
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Pointer to location in which to store the floating-point value of the
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expression.
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.AP int *booleanPtr out
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Pointer to location in which to store the 0/1 boolean value of the
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expression.
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.AP Tcl_Obj *resultPtrPtr out
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Pointer to location in which to store a pointer to the object
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that is the result of the expression.
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.BE
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.SH DESCRIPTION
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.PP
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These four procedures all evaluate an expression, returning
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the result in one of four different forms.
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The expression is given by the \fIobjPtr\fR argument, and it
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can have any of the forms accepted by the \fBexpr\fR command.
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.PP
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The \fIinterp\fR argument refers to an interpreter used to
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evaluate the expression (e.g. for variables and nested Tcl
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commands) and to return error information.
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.PP
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For all of these procedures the return value is a standard
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Tcl result: \fBTCL_OK\fR means the expression was successfully
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evaluated, and \fBTCL_ERROR\fR means that an error occurred while
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evaluating the expression.
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If \fBTCL_ERROR\fR is returned,
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then a message describing the error
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can be retrieved using \fBTcl_GetObjResult\fR.
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If an error occurs while executing a Tcl command embedded in
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the expression then that error will be returned.
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.PP
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If the expression is successfully evaluated, then its value is
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returned in one of four forms, depending on which procedure
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is invoked.
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\fBTcl_ExprLongObj\fR stores an integer value at \fI*longPtr\fR.
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If the expression's actual value is a floating-point number,
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then it is truncated to an integer.
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If the expression's actual value is a non-numeric string then
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an error is returned.
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.PP
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\fBTcl_ExprDoubleObj\fR stores a floating-point value at \fI*doublePtr\fR.
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If the expression's actual value is an integer, it is converted to
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floating-point.
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If the expression's actual value is a non-numeric string then
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an error is returned.
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.PP
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\fBTcl_ExprBooleanObj\fR stores a 0/1 integer value at \fI*booleanPtr\fR.
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If the expression's actual value is an integer or floating-point
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number, then they store 0 at \fI*booleanPtr\fR if
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the value was zero and 1 otherwise.
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If the expression's actual value is a non-numeric string then
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it must be one of the values accepted by \fBTcl_GetBoolean\fR
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such as ``yes'' or ``no'', or else an error occurs.
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.PP
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If \fBTcl_ExprObj\fR successfully evaluates the expression,
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it stores a pointer to the Tcl object
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containing the expression's value at \fI*resultPtrPtr\fR.
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In this case, the caller is responsible for calling
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\fBTcl_DecrRefCount\fR to decrement the object's reference count
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when it is finished with the object.
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.SH "SEE ALSO"
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Tcl_ExprLong, Tcl_ExprDouble, Tcl_ExprBoolean, Tcl_ExprString, Tcl_GetObjResult
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.SH KEYWORDS
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boolean, double, evaluate, expression, integer, object, string
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