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, 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. |
CONST |
char *string (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 string argument and return the result
in one of four different forms. The expression can have any of the forms accepted by the expr com-mand. command.
mand. Note that these procedures have been largely replaced by the object-based procedures Tcl_Expr-LongObj, Tcl_ExprLongObj,
LongObj, Tcl_ExprDoubleObj, Tcl_ExprBooleanObj, and Tcl_ExprObj. Those object-based procedures eval-uate evaluate
uate 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 expres-sion. expression.
sion. 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, depend-ing depending
ing on which procedure is invoked. Tcl_ExprLong stores an integer value at *longPtr. If the expres-sion's expression's
sion's actual value is a floating-point number, then it is truncated to an integer. If the expres-sion's expression's
sion'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 other-wise. otherwise.
wise. 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.
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.
SEE ALSO
Tcl_ExprLongObj, Tcl_ExprDoubleObj, Tcl_ExprBooleanObj, Tcl_ExprObj
KEYWORDS
boolean, double, evaluate, expression, integer, object, string
Tcl 7.0 Tcl_ExprLong(3)
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