Linux Manual Pages

Free Software * Books

Source Code

Free Media

Linux

Tcl_ExprLong

HOME

Tcl_ExprLong

NAME
SYNOPSIS
ARGUMENTS
DESCRIPTION
SEE ALSO
KEYWORDS

___________________________

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.

KEYWORDS

boolean, double, evaluate, expression, integer, object, string

Opportunity

Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.

Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.

Free Software

Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.

Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.

Free Books

The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.

Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.

Education

Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.

Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.