손으로 계산하는 긴자리 곱셈표 만들기 with F#

초등학교 때 배우던 두 정수의 곱셈표를 만들어 주는 F# 소스이다.
이 소스는 Python 소스를 F# 소스로 변환한 것이라 F#의 명령형 언어 특징을 위주로 짜여져 있다.

(*
 * Filename: MakeMultTable.fs
 *
 *     Print a multiplication table.
 *
 *  Compile: fsc MakeMultTable.fs
 *  Execute: MakeMultTable 230 5100
 *
 *     Date: 2010/07/15
 *   Author:  PH Kim   [ pkim ((AT)) scripts.pe.kr ]
 *)

#light

exception RuntimeError of string
exception ValueError of string

let println s =
    printfn "%O" s

let print s =
    printf "%O" s

let printUsage dummy =
    println "Using: python makeMultTable.py [number1] [number2]"
    println "Print a multiplication table for the given two integers."

let printMultTable x y =
    let mutable nx = x
    if nx < 0 then
        nx <- -nx
    let mutable ny = y
    if ny < 0 then
        ny <- -ny
    let mutable ntail1 = 0
    let mutable ntail2 = 0
    while (nx % 10) = 0 do
        nx <- nx / 10
        ntail1 <- ntail1 + 1
    while ny % 10 = 0 do
        ny <- ny / 10
        ntail2 <- ntail2 + 1
    let z = nx * ny
    let strZ = sprintf "%d" z
    let strX = sprintf "%d" nx
    let strY = sprintf "%d" ny
    let n = strY.Length
    let zeros  = "0000000000000000000000000000000000000000"
    let whites = "                                        "
    let bars   = "----------------------------------------"
    let loffset = "       "
    let line4 = loffset + strZ
    let line1 = loffset + (whites.Substring(0, strZ.Length - strX.Length)) + strX
    let line2 = "   x ) " +  (whites.Substring(0, strZ.Length - strY.Length)) + strY
    let line3 = "     --" +  (bars.Substring(0, strZ.Length))
    println (line1 + (zeros.Substring(0, ntail1)))
    println (line2 + (zeros.Substring(0, ntail2)))
    println line3
    if strY.Length > 1 then
        for i in 0..(strY.Length - 1) do
            let y1 = int (strY.Substring(strY.Length - i - 1, 1))
            if not (y1 = 0) then
                let strT = sprintf "%d" (nx * y1)
                println (loffset + (whites.Substring(0, strZ.Length - strT.Length - i)) + strT)
        println line3
    println (line4 + (zeros.Substring(0, ntail1)) + (zeros.Substring(0, ntail2)))

// Begin here
let cmdArgs = System.Environment.GetCommandLineArgs()
if (Array.length cmdArgs >= 3) then
    let x = int (cmdArgs.[1])
    let y = int (cmdArgs.[2])
    println ""
    printMultTable x y
else
    printUsage 0
    exit(1)

컴파일> fsc MakeMultTable.fs

실행> MakeMultTable 230 5100
결과>

         230
   x )   5100
     ------
         23
       115
     ------
       1173000