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 value-
based procedures Tcl_ExprLongObj, Tcl_ExprDoubleObj,
Tcl_ExprBooleanObj, and Tcl_ExprObj. Those value-based procedures
evaluate an expression held in a Tcl value instead of a string. The
value 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
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 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, value, string

Tcl 7.0 Tcl_ExprLong(3)