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.
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 object-based procedures
Tcl_ExprLongObj,
Tcl_ExprDoubleObj,
Tcl_ExprBooleanObj,
and
Tcl_ExprObj. 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.
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, object, string