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Gnymph v0.1

Joe Bentley
rbentley@atlas.kennesaw.edu
15 Jan 2007

Gnymph is a visual, object-oriented, general purpose dataflow programming language that runs under Linux. Users can edit a set of diagrams to describe their program, step through the diagrams to trace program execution and remove any bugs, then compile those diagrams to C source. It reduces development time, improves documentation, and puts tools for the collaborative creation of software into the hands of visually-oriented end users.

Caveat: This is very much pre-alpha software. It can immediately be useful for making dataflow diagrams and visualizing program structure, however, its current status as a compiler only shows where I'm going. There is also a great deal of unorganized and unedited documentation for the source; it's not included with this release because I have to first remove the self-contradictory parts.

It is released under GPL version 2.

Contents

Starting

To start Gnymph:

Building Gnymph requires that the development files for gtk2 have been installed.

Schematics

The primary edit space of Gnymph is the schematic. This is a scrollable canvas on which the user can place and connect chips. It can be scrolled a small amount with the arrow keys. It can be scrolled a page at a time with PgUp | PgDn | Shift-PgUp | Shift-PgDn. Right drag in space will scroll the schematic with the mouse. Return to the origin with Home.

There are three main types of schematics. The program schematic is unique and is at the top of the hierarchy. It can include classes, static methods, global variables, and methods to get and set those global variables.

Figure 1: Class hierarchy of Gnymph in Gnymph

The class schematic defines a class. It can include all the items that can appear in the root schematic, including classes. It can also include class methods, instance attributes, get and set methods for instance attributes, and a constructor and destructor. Double-clicking on a class icon will display and edit the schematic for that class.

Figure 2: The Point class in Gnymph

Method schematics define the implementation of static methods, class methods, get and set methods for globals and instance attributes, constructors, and destructors. They each have one input bar and one output bar. They also have a set of chips through which data flows between the input and output bars. Double-clicking on a method icon will display and edit the schematic for that method.

Figure 3: Method to compute Pythagorean distance (click for code)

Chips

The primary visual element on the schematic is the chip. A chip is created by clicking in the schematic background. The chip can be moved by left down on the chip and dragging. It can be deleted with clipboard operations Cut or Clear.

Figure 4: Anatomy of a chip

Each chip has a Type icon. This identifies what the chip is. On the left of the type icon is an optional object input terminal; on the right is an optional object output terminal. The datum to use as 'self' comes in on the object input. If the object input terminal does not exist, then the current 'self' is used.

Above the type icon may appear an IO-bar. On the left of the IO-bar are the regular input terminals; on the right are the regular output terminals. An IO-bar is created by right down in the type icon and dragging directly up. It can be resized by a right down in the IO-bar and dragging up or down.

Below the type icon is an optional enable icon. It determines whether or not the chip executes and outputs a value when the chip does execute. On the left is an optional enable input terminal; on the right is an optional enable output terminal. An enable icon is created by right down in the type icon and dragging directly down. It can be removed by right down in the enable icon and dragging directly up.

Below the enable icon if present or the type icon if not is an optional chip name. It is given a default value when the chip is created. It can be changed by left clicking on it; this puts Gnymph in a text editing mode. Some names are special; these are hidden and the type icon changed to a specific image. For instance, if the name of a call is changed to '+', then the name is hidden and the icon type is changed to the addition symbol.

If the chip name is not present then an inject icon is present in its place. It has exactly one input terminal on its left. It specifies that the name of the chip will be determined at runtime. The name is provided on the input terminal. An inject icon is created by setting the name to the empty string. It can be removed by right clicking on the icon. In this case, a default name will be assigned to the chip.

Connections between terminals can be created by left down on the source terminal and left up over the target terminal. An input can only be connected to an output. Inputs cannot be connected together, nor can outputs be connected together. A connection can be removed by repeating the connection process: left down on one end of the connection and left up on the other end.

The chip and every pin on it can have an optional comment. This is a multi-line text string. It is created by left clicking on the item while the Control key is held down. This creates a comment with a default value. It can be removed by setting the comment text to the empty string. Comments have a position relative to their owner pin or chip. This relative position can be changed by left down on the comment and dragging.

Selections

A single chip can be selected by left clicking on it. Multiple chips can be selected by dragging an area in the schematic; all chips (if any) inside the drag rect are selected. Chips can be added to a selection by holding down the Shift key while selecting. A selection can be cancelled by right clicking in space or by pressing Escape.

In general, performing an operation (such as changing the chip type or adding a particular pin) will apply to all chips in the selection.

When text is being edited, a portion of the text can be selected by left down in the text area and dragging.

Menus

Popup menus are brought up by right clicking. They display as a circle with wedges and a cancel disk in the middle. Left clicking on the cancel disk will make that level of the menu go away without selection. As the mouse moves around the wedges, the current wedge is highlighted. Left clicking on a wedge will select that icon and finish the menu. Right clicking on a wedge will pull up a submenu if a submenu exists for that icon.

Figure 5: Popup chip type menu


Figure 6: Selecting a Mux from a submenu

Right clicking on the type icon of a chip brings up the chip type menu. If a selection is made, then the chip type will change to the selection. Right clicking in space when there is no selection will select the default chip type to use when creating chips.

Right clicking on a pin will bring up the pin type menu to select the type of the pin. Right clicking in a pin area but not on a pin will select the default type of the pin to create. Available pin types are

An extreme example of what's possible with terminal annotations is given in the following figure. It also demonstrates variable arity and runtime name injection.

Figure 7: Lots of lists (click for code)

Right clicking on an enable icon will bring up the enable type menu. Available enable types are

Chip Type Icons

These icons can be used in the root schematic

These icons can be used in a class schematic

The remaining icons can only be used in method schematics.

Control structures

Exceptions

Logic

Math

List

Toolbar

The toolbar is split into three tool groups. The left tool group is for browser functionality:

The middle tool group is for clipboard and editing operations:

The right tool group is for system operations:

Examples

A recursive implementation of the factorial function is shown in Figure 8. The chip on the far left is the input bar; the chip on the far right is the output bar. The chip on the left of the output bar is a Mux. Its bottom input is a control input. Mux and Demux allow for conditional execution in Gnymph. They try to execute as little of the method as possible. The code to produce the control input for the Mux is first executed. If it is true, then the construction of the integer 1 will not be needed so it will not execute. If it is false, then the decrement, recursive call, and multiply that lead to the true input are not needed and will not execute.

Figure 8: Recursive implementation of factorial

Pseudocode in a traditional language

	if X <> 0 then
		return X * factorial( X - 1 )
	else
		return 1

Figure 9 gives an iterative version of the same problem. The loop executes once for each iteration of the input. The product is initialized to 1. Each iteration of the loop multiplies the product by the next integer value. The inputs to the Loop-end are copied back to the Loop-begin. The last value to appear on the lower output of the Loop-end is returned.

Figure 9: Iterative implementation of factorial

A simple version of bubble sort is shown in Figure 10. Here the size attribute is retrieved and compared against the constant 2. The result is used as a control input to a Mux. If there are two or less items in the input list, then the pair is ordered and returned. Otherwise, the tail of the input list is bubble sorted, and then the head is inserted into the list in order.

Figure 10: Bubble sort