Tcl_ExprLong(3Tcl)Tcl_ExprLong(3Tcl)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 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.
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.
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Tcl_ExprLong(3Tcl)Tcl_ExprLong(3Tcl)
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 *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
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