In f #, is there a language construct for testing if a number is between two other numbers (in a range)?

Question

In f # I am looking for a more succinct equivalent:

myNumber >= 2 && myNumber <= 4 

I imagine something like

 myNumber >=< (2, 4) 

Is there some kind of operation like this?

Answer 1

There is no operator of your own, but you can define your own.

 let inline (>=<) a (b,c) = a >= b && a<= c 

Answer 2

John's answer is exactly what you asked for, and the most practical solution. But I wondered if the operator (s) could be defined so that the syntax came close to normal mathematical notation, i.e. a <= b <= c .

Here is one such solution:

 let inline (<=.) left middle = (left <= middle, middle) let inline (.<=) (leftResult, middle) right = leftResult && (middle <= right) let inline (.<=.) middleLeft middleRight = (middleLeft .<= middleRight, middleRight) 1 <=. 3 .<=. 5 .<= 9 // true 1 <=. 10 .<= 5 // false 

A few comments about this:

• I used the symbol . to indicate the "average" expression
• . was a very deliberate choice and is not easily replaced by other other characters that you like better (for example, if you might like the look 1 < =@ 3 @<= 5 better). The F # compiler changes the associativity and / or priority of the operator based on the character of the first character of the operator . We want a standard rating / short circuit from left to right as well . allows it.
• Comparison of 3-dimensional numbers is fully optimized, but comparison with 4 digits leads to the fact that the IL-code selects tuples and performs various other operations that are not absolutely necessary:

Answer 3

Is there some kind of operation like this?

Great question! The answer is no, no, but I wanted it to be.

The answer to Latin is good, but it is not designed for short circuit. Therefore, if the first test fails, the remaining subexpressions are still evaluated, although their results are not relevant.

FWIW, in Mathematica you can do 1<x<2 just like math.