GE - Greater/Equal Test

Usage

	logical = GE ( npt1 npt2 )
	res = GE ( npt1 npt2 truept falsept )

Parameters

	logical	Logical:TRUE or FALSE depending on the result of the comparison.
	npt1	A numerical point.
	npt2	A numerical point.
	truept	An optional point to be returned if npt1 is greater than or equal to npt2.
	truept	An optional point to be returned if npt1 is not greater than or equal to npt2.

Description

This module returns true if the first argument is greater than or equal to the second and false otherwise. GE may also be used in a four value mode, see EQ for a description.

See Real for details on comparing floating point numbers.

Examples

	GE(100 Real:100.2)	results in Logical:FALSE
	GE(100 Real:100.2 hohoho boohoo)	results in NId:boohoo
	GE(10 5 @{1 + 2} @{3 + 4})	results in Int:3 (use quote to prevent unneccessary evaluations)

Geo - Perform Geocoordinate Functions

Usage

value = Geo ( geo1 [[geo2] geo3] tag )

Parameters

	geo1	A geocoordinate
	geo2	An optional second geocoordinate
	geo3	An optional third geocoordinate
	tag	One of the optional tagged arguments

Tagged Arguments

	Dawn::date	Returns the approximate time of dawn/sunrise for date and the location specified in the first argument.
	Distance::fraction	Returns the geocoordinate between the two coordinates that is a fraction of the distance between the two. The fraction is a number between 0 and 1 with 0 representing the first coordinate and 1 the second. A fraction of 0.5 represents halfway between the two.
	Dusk::date	Similar to Dawn but returns the time of dusk/sunset.
	Grid::num	Determines the position of geo1 within a grid of num by num cells with an upper left corner defined by geo2 and a lower right corner defined by geo3. If num is an Int2 point then the first number is the number of rows in the grid and the second is the number of columns. The result is an Int2 point of the form Int2:<row column>.
	LunarAltitude::cal	Returns the lunar altitude at the location specified by geo1 at the date-time given by cal. The result varies between -180 and +180 degrees. Moon rise and moon set correspond to zero degrees. If the first argument is a UDate or DateTime point then it is with respect to GMT, not local time.
	UOM::units	Specifies the unit-of-measure when Distance? is requested. The units value is determined by the entries in v4LanguageInfo.v4i in the v4_home directory. For English, the default units are M and MTR for meters, KM for kilometers (default), MI and MILES for miles, FT and FEET for feet, YD and YARDS for yards, NM and NMILES for nautical miles. Conversion to other units-of-measure can be found here.

Tagged Results

	Direction?	Return the direction (from north) of the second geocoordinate with respect to the first. The result is in degrees.
	Distance?	Return the distance between the two geocoordinates. The unit-of-measure can be set with the UOM tag option. The default is kilometers.

Description

This module performs various operations on its arguments.

Note that for the Dawn and Dusk options a complete geocoordinate is necessary (i.e. one with latitude, longitude, elevation, and time zone). The elevation is defaulted to 0 and the time zone is approximated from the longitude if missing.

	Geo(G:(40 01.052N 75 15.613W) G:(40 04.476N 75 24.630W) Distance?)	results in Num:14.2798625581959
	Geo(G:(40.1 -88.2) G:(21 25N 39 49E) Direction?)	results in Num:40 - the direction from Urbana IL to Mecca
	Geo(G:(40.0209 -76.26 150) Dawn::UDate:030320)	UCal:20-Mar-2003:06:07:03 - the time of dawn in Philadelphia,PA on 20-Mar-2003
	Geo(G:(40.2723 75.7620) G:(39.8187 74.8838) distance::0.50)	G:(40.0447 75.325 0 -)

GraphConnect - Connect Two Nodes on a Graph

Usage

	result = GraphConnect ( list tagarg )
	result = GraphConnect ( tagarg )

Parameters

result

The result varies on the arguments. It may be a list of nodes, or a list of lists when there are multiple connections.

Tagged Arguments

	AWhile::logical	Evaluate logical after each point in the Enum list. If the result of the evaluation is true then continue otherwise terminate. Note that this argument is tested after each point. While::isct is used to test before each point.
	Begin::node	Defines the starting node for the connection
	Context::point	For each enumeration point, V4 evaluates and inserts the point into the current context. If the point is UV4:none then nothing is done (i.e. UV4:none is not placed into the context). This point can be inserted into the context by quoting it: Context::@UV4:none. If point is UV4:Skip the current point is ignored entirely.
	ContextP::point	This is identical to the Context tag except that if point evaluates to a list then each point in the list is inserted into the context.
	Depth::num	Limits the depth of the connection to a maximum of num nodes.
	Distance::dim	The total path distance is 'returned' as a point in the context on dimension dim. This dimension must be of type Integer or Real. This option only applies when performing the traveling salesman analysis.
	Edge::node	Defines the start and end nodes of an edge. The first Edge defines the beginning node and the second occurrence defines the ending node. At least two Edge arguments must be given. Any more than two assumes that the next edge is connected to the prior.
	End::node	The ending or target node in the connection.
	Enum::list	The edges of the graph are to be determined by iterating through the list and evaluating the Edge points for each element of the list.
	If::logical	Used in conjunction with the Enum argument to restrict points to those in which logical evaluates to TRUE.
	Maximum::weight	Specifies the weight of an edge and that the best connection between the start and end nodes is one that maximizes this weight.
	Metric::logical	If TRUE (default) then distances on traveling salesman analysis with geocoordinates are in kilometers, if FALSE then in miles.
	Minimum::weight	Similar to Max except that the best connection is the one minimizing the edge weights.
	OneWay::logical	If this tag is given then it is evaluated for each edge in the graph. If the evaluation of logical is TRUE then the edge is considered to be one-way. If it is FALSE or the OneWay tag is not given then the edge is assumed to be two-way.
	Parent::pt	Specifies the parent point. See Enum for a complete description.
	PIf::isct	Specifies a test based on the parent. See Enum for a complete description.
	Result::num	Return up to a maximum of num resultant connections.
	Route::num	The number of iterations to optimize on traveling salesman route through all nodes.
	Until::isct	isct is evaluated for each point in the list. If the result is false, then Enum continues. If it is true, Enum immediately stops processing the point and all subsequent points.
	While::isct	isct is evaluated for each point in the list. If the result is true, then Enum continues. If it is false, Enum immediately stops processing the point and all subsequent points.
	X::isct	isct is evaluated for each point in the list to obtain the X coordinate of a node (Traveling Salesman Analysis only).
	Y::isct	isct is evaluated for each point in the list to obtain the Y coordinate of a node (Traveling Salesman Analysis only).

Description

This module performs two basic analyses. The first is determining a path from one point on a graph to another. The second type of analysis is know as the Traveling Salesman Problem. This analysis returns the shortest path to take to visit all nodes in a graph. Note that the algorithm used is not guarenteed to return the theoretical shortest path as this becomes prohibitively expensive as the number of nodes increases (on the order of N! where N is the number of nodes!). See the Wikipedia article or here for more information on the general problem.

This first use of this module is as a generalized function for finding one or more connections in a graph. The edges of a graph may be weighted with the search returning connections with minimal and/or maximal weights. The module can search for several min/max solutions at once. Typical uses include finding the shortest (in time or distance) path between two points in a geocoordinate database.

The traveling salesman analysis is triggered when the Route option is given. This specifies the number of iterations to take to find the shortest path. The greater the number of iterations, the better the chances of getting the optimal solution. The handling of nodes is slightly different in this mode of the function. The iterating list can take on three different forms. If the elements are Int2 points then they are assumed to be points on an X-Y plane. If the elements are Geocoordinates then those are the assumed positions of the nodes. Any other type of point is injected into the context and the X and Y arguments are evaluated to obtain the X and Y coordinates for that node.

	[Nodes] ( Int2:<3 4> :<1 1> :<6 6> :<3 2> :<5 5> :<0 5> :<1 3> :<6 2> :<3 6> :<4 3>)	Define a set of points on an X-Y plane
	GraphConnect([Nodes] Route::10 Distance::Num)	Calculate shortest path and return as a list, Num updated with total path length*
	List([Nodes] Nth::Int*)/GraphConnect([Nodes] Route::10)	Same as above but list the X-Y positions

GT - Greater/Than Test

Usage

	logical = GT ( npt1 npt2 )
	res = GT ( npt1 npt2 truept falsept )

Parameters

	logical	Logical:TRUE or FALSE depending on the result of the comparison.
	npt1	A numerical point.
	npt2	A numerical point.

Description

The GT module returns logical true if the first argument is greater than the second.

See Real for details on comparing floating point numbers.

Examples

GT(100 Real:100.2)

Logical:FALSE

GuiAlert - Display an alert box with message

Usage

value = GuiAlert ( message )

Parameters

	value	This module always returns Logical:True.
	message	The message to be displayed.

Description

This module opens up an alert window displaying the specified message. The user must click the OK button in the window to close the window and resume the V4 process. If multiple arguments are given then they are concatenated into a single message string.

Currently this module is supported only on Windows-based operating systems.

Examples

GuiAlert(Str("The value of Student* is " Student*))

GuiAlert("The value of Student* is " Student*)

same as above

GuiMsgBox - Display a popup message window

Usage

button = GuiMsgBox ( tag )

Parameters

	button	A point on Dim:UV4 indicating which button was clicked to close the window. The value will be one of the following: ABORT, CANCEL, IGNORE, NO, OK, RETRY, or YES.
	tag	One or more of the following tagged arguments.

Tagged Arguments

	Filter::list	A list of lists used with the FileOpen and FileSave message box types. Each element of list must itself be a list containing two components: the first being a text description and the second being a file extension. These extensions and corresponding descriptions appear in the file open box as possible selection filters.
	Icon::type	Defines the type of icon to be displayed in the window. type must be one of: Exclamation, Hand, Information, Question, or Stop.
	Message::text	The message to be displayed in the window. A non-tagged text string is also assumed to be the message.
	Title::text	The window title, the default value is V4 Message.
	Type::type	Determines the type of message box and buttons available to close the window. The type must be one of: AbortRetryIgnore, OK, FileOpen, FileSave, RetryCancel, YesNo, or YesNoCancel.

Description

The GuiMsgBox module pops up a message box and suspends V4 processing until the user acknowledges and closes the window. The value returned is determined by the button clicked by the user to close the window.

Currently this module is supported only on Windows-based operating systems.

Examples

GuiMsgBox("Do you want to continue?" Type::YesNo)

Returns UV4:Yes or UV4:No depending on the user's response. Note that a non-tagged text string is assumed to be the message.