ExprLong
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NAME
Tcl_ExprLong, Tcl_ExprDouble, Tcl_ExprBool, 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.
char *string (in) Expression to be
evaluated. Must be in
writable memory (the
expression parser makes
temporary modifications
to the string during
parsing, which it
undoes before
returning).
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 an expression, returning
the result in one of four different forms. The expression
is given by the string argument, and it can have any of the
forms accepted by the expr command. 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. Interp->result is assumed to be
initialized in the standard fashion when any of the
procedures are invoked.
For all of these procedures the return value is a standard
Tcl result: TCL_OK means the expression was succesfully
evaluated, and TCL_ERROR means that an error occurred while
evaluating the expression. If TCL_ERROR is returned then
interp->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 Tcl_ExprBoolean stores 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 interp->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.
KEYWORDS
boolean, double, evaluate, expression, integer, string