Examples

small programs that do interesting things

While we’ve given short examples of MiniScript code throughout this manual, this chapter presents several longer, more interesting examples. Many of the tasks illustrated are taken from RosettaCode, an online database of programming challenges with solutions in many languages. You can go there to compare the MiniScript solution to any other language; you may be amazed how much more readable MiniScript is than the alternatives.

FizzBuzz

FizzBuzz is a standard introductory-level programming challenge . The task is simple: print 1 the numbers 1 through 100, but: for multiples of three, print “Fizz” instead of the number; for multiples of five, print “Buzz” instead of the number, and for any number that’s a multiple of three and five, print “FizzBuzz”.

There are clearly many ways to tackle this; here’s one.

fizzBuzz = function(n)
     for i in range(1, n)
      s = "Fizz" * (i%3==0) + "Buzz" * (i%5==0)
      if s == "" then s = str(i)
      print s
end for
end function
fizzBuzz 100

Instead of just hard-coding a loop from 1 to 100, we’ve made a function that can FizzBuzz up to any number. Within that function, the only clever bit is line 3, which takes advantage of a couple of MiniScript features. First, comparisons (such as i%3==0 — read “i mod 3 equals zero”) evaluate to 1 when true, or 0 when false. Second, you can multiply a string by a number to repeat it that many times. This means that if you multiply a string by a condition, you get either the original string (if the condition is true) or the empty string (if it is false).

That lets us easily generate “Fizz”, “Buzz”, and “FizzBuzz” depending on what our loop counter is divisible by. Line 4 simply fills in the number if we don’t get one of those strings. (Quiz: can you rewrite this line to use the same multiply-by-condition trick as line 3?)

Filter

Here’s another RosettaCode task : select certain elements from an Array into a new Array in 2 a generic way. To demonstrate, select all even numbers from an Array.

filter = function(seq, f) // filter seq to where f is true

result = []
for i in seq
if f(i) then result = result + [i]
end for
return result

end function
isEven = function(x)
return x % 2 == 0
end function
list = [2,3,5,6,8,9]
print filter(list, @isEven)

This is a pretty straightforward conversion of the task description into MiniScript code. Our filter function takes a list and a function, and builds a new list by appending each element where the function, applied to that element, is true.

We illustrate by making an isEven function that returns true only when its argument mod 2 is zero (i.e., the argument is evenly divisible by 2). Then we pass @isEven to find just the even elements of a given list.

Greatest Common Divisor

Here’s a function that finds the biggest number that can divide evenly into two given numbers . Middle schoolers everywhere will soon be out of work.

gcd = function(a, b)
     if a == 0 then return b
     while b != 0
        newA = b
        b = a % b
        a = newA
     end while
     return abs(a)
end function
print gcd(-21, 35)

The algorithm here, known as the “Euclidian algorithm for finding the GCD,” is clever. The actual MiniScript code is simple.

Maximum Element

MiniScript does not have a standard intrinsic for finding the maximum element of a list. But you can easily add it yourself, using this code.

. max = function(seq)

max = function(seq) 
     if seq.len == 0 then return null
     max = seq[0]
     for item in seq
        if item > max then max = item
     end for
     return max
     end function
print max([5, -2, 12, 7, 0])

Pretty simple stuff. Line 2 checks to make sure the sneaky user hasn’t given us an empty list; if they have, we return null, as there is no sensible max in that case. Otherwise, we just suppose it’s the first element, and then loop over each element in the list, keeping the biggest.

Notice that the max variable assigned to on line 1 is in the global variable space, while the max assigned on lines 3 and 5 (and then returned on line 7) is local to a function. These happen to have the same name, but have nothing to do with each other. As a matter of style, it might have been better to name the local variable result rather than max. But it seemed like a good opportunity to demonstrate how local and global variables are separate, even if they have the same name.

Titlecase

MiniScript has intrinsics to convert a string to all upper- or lower-case letters. But what if you want to capitalize just the first letter of each word, and lowercase the rest?

titlecase = function(s)
     result = ""
     for i in s.indexes
        if i == 0 or s[i-1] == " " then
             result = result + s[i].upper
        else
             result = result + s[i].lower
        end if
     end for
     return result
end function
print titlecase("SO LONG and thanks for all the fish")

We just iterate over the string, capitalizing each letter that is either the very first character in the string, or is preceded by a space, and lower-casing the rest.