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Tcl_ExprLong(3tcl) Tcl Library Procedures Tcl_ExprLong(3tcl) 





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
    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







  

    7.0
    Tcl