Tcl_ExprLong(3) Tcl Library Procedures Tcl_ExprLong(3)_________________________________________________________________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.
char *string (in) Expression to be
evaluated. Must be
in writable memory
(the expression
parser makes tempo-
rary modifications to
the string during
parsing, which it
undoes before return-
ing).
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.
_________________________________________________________________Tcl 7.0 1
Tcl_ExprLong(3) Tcl Library Procedures Tcl_ExprLong(3)DESCRIPTION
These four procedures all evaluate an expression, return-
ing 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 com-
mands) 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 successfully
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 *dou-
blePtr. 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 float-
ing-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
Tcl 7.0 2