Tcl_ExprLong(3) Tcl (7.0) 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, 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 or objPtr.
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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Tcl_ExprLong(3) Tcl (7.0) Tcl_ExprLong(3)
DESCRIPTION
These four procedures all evaluate the expression given by
the string 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 object-based procedures
Tcl_ExprLongObj, Tcl_ExprDoubleObj, Tcl_ExprBooleanObj, and
Tcl_ExprStringObj. Those object-based procedures evaluate
an expression held in a Tcl object instead of a string. The
object 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. interp->result
is assumed to be initialized in the standard fashion when
they 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 *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 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
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Tcl_ExprLong(3) Tcl (7.0) Tcl_ExprLong(3)
Tcl_ExprString calls Tcl_PrintDouble to convert it to a
string.
SEE ALSO
Tcl_ExprLongObj, Tcl_ExprDoubleObj, Tcl_ExprBooleanObj,
Tcl_ExprObj
KEYWORDS
boolean, double, evaluate, expression, integer, object,
string
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