Tcl_ExprLong(3tcl) Tcl Library Procedures Tcl_ExprLong(3tcl)
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NAME
Tcl_ExprLong, Tcl_ExprDouble, Tcl_ExprBoolean, Tcl_ExprString - evalu-
ate 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 ex-
pression.
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 ar-
gument and return the result in one of four different forms. The ex-
pression 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 ex-
pression (e.g. for variables and nested Tcl commands) and to return er-
ror 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_Ex-
prLong 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 ex-
pression'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 ex-
pression'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(3tcl)
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