2.1 Taskell: the Haskell implementation in Tamgu (en)

Tamgu is a Functional Language

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Tamgu is a real functional language. Unlike many languages that integrate functional features, Tamgu offers a real functional formalism that works in parallel with the rest of the code.

You can write your functions, data structures and call them from your Tamgu program.

Taskell

Taskell is a relatively faithful transformation of Haskell to adapt it to Tamgu.

First of all, a Taskell expression is always enclosed with <...>. You can easily and usefully use these expressions to write lambdas.

For example, Taskell's "map" operator applies an operation to a vector.

vector v = <map (+1)[1..10]>;

The line above will stow in v the values: [2,3,4,5,6,7,8,9,10,11].

Most of Haskell's operators have been integrated: filter, take, takeWhile, takeWhile, fold etc.

Iterate

You can also iterate on an external vector to perform your own operations:

vector v =[1..10];
vector vv = < x*2 | x <- v>;

Check Values

Your expression can also be used to filter out some values:

vector v =[1..10];
vector vv = < x*2 | x <- v, odd(x)>;

In the above example, we only keep and compute odd values.

Functions

A function is declared as follows:

<addstr(x,y) = x+y>

Typing

To type the parameters, you must declare before declaring your function, a structure that describes what the function receives and what it returns:

<addstr:: string -> string -> string -> string>
<addstr(x,y) = x+y>

In the description above, we indicate that the function takes two strings as input and returns a string.

Let's take an example:

We will implement the function: joined which transforms a vector into a string.

<joined:: vector -> string>
<joined(v) = x | x <- v>

Data Structures

Taskell also accepts data structure definition together with their derivations and their methods. Below is an example of a piece of code that computes the right surface for the right object:

// -- We first create a Shape object with two derivations: Circle and Rectangle
// -- They can display their content hence "Show"

<data Shape = Circle float float float  | 
              Rectangle float float float float
              deriving (Show)>

// -- A Surface takes a Shape as input and returns a float
<Surface :: Shape -> float>
<Surface(Circle _ _ r) = 2π×r²> // -- only the radius is useful
<Surface(Rectangle x y xx yy) = abs(xx-x) × abs(yy-y)>


float c=Surface(<Circle 10 20 30>); // -- we compute the surface for a circle

float r=Surface(<Rectangle 20 20 40 40>); // -- we compute the surface for a rectangle