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Programming language: Haskell
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This software is intended to help a developer designing electronic circuits by describing them with arrows. The arrow notation represents the according. From the netlist the developer can generate various other formats by compiling the arrow into them. With this software three basic compilers are shipped. One generates a simple textual representation that helps debugging the actual circuit. Another generates VHDL representations of the circuit. The third one generates DOT syntax for visualization of circuits.


The Software is available of various locations. The source is downloadable via http://hackage.haskell.org/package/ArrowVHDL-1.1/ArrowVHDL-1.1.tar.gz It's git archive can be cloned with the following command:

> git clone https://github.com/frosch03/arrowVHDL.git

Another way of installing this software is via haskell's package management system cabal:

> cabal update
> cabal install ArrowVHDL

This software is intended too be used interactively within ghci. Therefore no further setup is necessary.

Basic Functionality

There is a canon of functions to be used, while working with netlists. These are

  • flatten - With flatten one is able to extract atomic parts from a netlist. This function should be used with all more complex circuits to ensure the generation of meaningful netlists.
  • synthesize - This function actually compiles the netlist arrow into one of the description languages. The result for complex netlists must then be feed into flatten to get a meaningful netlist.
  • simulate - With simulate the callable part of the circuit arrow is extracted. To actually run a simulation of the circuit over a given input stream, the runStream function is needed.
  • runStream - This function must be used to create a function that operates over a list of values of the type the circuit arrow expects.


Load up the example file Beispiel.hs into an interactive ghci session via:

ghci Beispiel.hs
Ok, modules loaded: ...

You can then go through the examples defined within Beispiel.hs.

Data Types

At first one should have a look onto the type of the given example circuit.

Beispiel> :t aTest0
aTest0 :: (Arrow a, Num c) => Grid a c c

The circuit represents a "times two" circuit. Therefore it's type represents that every number c is mapped onto another number c. The circuit consists of a duplication part connected to an addition circuit.


To simulate that circuit over a list of input values one has to call simulate on aTest0 and pass that result into the runStream function. The resulting function can than applied to a list of input values:

Beispiel> (runStream (simulate aTest0)) [1..10]

As Haskell supports infinite lists, one could simulate the execution of the defined circuit over an infinite number of input values. Of course such a simulation would take forever. To actually simulate over infinite input values one has only to supply the circuit with an infinite list of Haskell:

Beispiel> (runStream (simulate aTest0)) (repeat 23)

Code Generation

To generate code from arrows one could use the supplied command synthesize. This function takes an arrow into another representation of that arrow. The actual supported variants could be graphviz's dot-notation as well as vhdl code. The process of synthesizing is done by

Beispiel> (synthesize aShiftR5_XorKey)

According to the way, the ArrowVHDL library generates netlists from the arrow description, the above instruction would only return the last step of the combined netlist. To create a meaningful description one needs to feed the result of the command into the flatten function

Beispiel> (flatten (synthesize aShiftR5_XorKey))

This will then return a complete netlist described within the selected description method.

Switching Describing Methods

For the lack of a better process, the switch of the describing method must be done manually by changing the included Show library. Therefore one must open the Show.hs file within the folder ./System/ArrowVHDL/Circuit/.

Within that file, there are three import statements for the different show mechanisms; two of them commented. Uncomment the desired method and comment the other two, like if one wants to output VHDL source, the import statements should look like the following

-- import System.ArrowVHDL.Circuit.Show.Simple
import System.ArrowVHDL.Circuit.Show.VHDL
-- import System.ArrowVHDL.Circuit.Show.DOT

After that, the ArrowVHDL library is again ready to use. It will now generate it's output within the selected format.

If there are for any reason more then one Show methods selected, one will get an Ambiguous occurrence error:

Ambiguous occurrence ‘showCircuit’
It could refer to either ‘Simple.showCircuit’,
imported from ‘System.ArrowVHDL.Circuit.Show....

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