`==, !=, >, >=, <, =<` are infixed operators.

`a==b` tests the equality between `a` and `b` and returns `1`
if `a` is equal to `b` and `0` otherwise.

`a!=b` returns `1` if `a` and `b` are different and `0`
otherwise.

`a>=b` returns `1` if `a` is superior or equal to `b`
and `0` otherwise.

`a>b` returns `1` if `a` is strictly superior to `b`
and `0` otherwise.

`a<=b` returns `1` if `a` is inferior or equal to `b` and
`0` otherwise.

`a<b` returns `1` if `a` is strictly inferior to `b`
and `0` otherwise.

To write an algebraic function having the same result as an
`if...then...else`, we use the boolean function `ifte`.

For example :

defines the boolean function *f* such that `f(x)= true` if
*x* ∈ ]0;+∞[ and `f(x)=false` if *x* ∈ ]−∞;0].

Input :

Output :

**Look out !**

`a=b` is not a boolean !!!!

`a==b` is a boolean.