F# 4.0 Design Patterns

Recursive function basics

In this chapter, I want to introduce you to the basics of recursive functions, leaving more detailed consideration for the more advanced contexts. At this point, I want to show how the F# default treatment of functions as non-recursive differs from a forced one when the function is explicitly declared recursive using the let binding modifier, rec.

Take a look at the following far-fetched snippet (Ch3_8.fsx):

let cutter s = 
  let cut s = 
    printfn "imitator cut: %s" s 
  let cut (s: string) = 
    if s.Length > 0 then 
      printfn "real cut: %s" s 
      cut s.[1..] 
    else 
      printfn "finished cutting" 
  cut s 

The cutter function here provides a non-empty string that's supposed to cut it from the left-hand side, symbol by symbol, until the argument is ...