Nim Tutorial Part1

.gitignore

nimcache

block_stmt.nim

#
# break         -> leaves the loop
# break [block] -> leaves the loop for block
#
block myblock:
  echo "entering block - break"
  while true:
    echo "looping - break"
    break # leaves the loop, but not the block
  echo "still in block - break"

block myblock2:
  echo "entering block"
  while true:
    echo "looping"
    break myblock2 # leaves the block (and the loop)
  echo "still in block"

check_digit.nim

import strutils, sequtils, parseopt

type NumberSet = tuple[odd: seq[int], even: seq[int]]

type CheckDigitResult = tuple[input: string, check_digit: int]

proc isOdd(n: int): bool =
  n mod 2 == 0

proc collectNumbers(number: string): NumberSet =
  var odd_numbers, even_numbers: seq[int] = @[]

  for pos in 0..(len(number) - 1):
    let next = pos + 1
    let v = parseInt(number[pos..pos])
    if isOdd(next):
      odd_numbers.add(v)
    else:
      even_numbers.add(v)
  (odd: odd_numbers, even: even_numbers)


proc checkDigit(number: string): CheckDigitResult =
  let numbers = collectNumbers(number)
  let odd_sum = foldl(numbers.odd, a + b)
  let even_sum = foldl(numbers.even, a + b)
  let odd_even_sum = odd_sum + (even_sum * 3)

  let str_num = intToStr(odd_even_sum)
  let last_index = len(str_num) - 1

  let last_num = parseInt(str_num[last_index..last_index])

  var check_digit = 0
  if last_num == 0:
    check_digit = 0
  else:
    check_digit = 10 - last_num

  (input: number, check_digit: check_digit)

proc writeHelp(): void =
  echo "help"
  quit(QuitSuccess)

proc writeVersion(): void =
  echo "1.0.0"
  quit(QuitSuccess)

for kind, key, val in getopt():
  case kind
  of cmdArgument:
    continue
  of cmdLongOption, cmdShortOption:
    case key
    of "help", "h": writeHelp()
    of "version", "v": writeVersion()
  of cmdEnd: assert(false)

while endOfFile(stdin) == false:
  let number = readLine(stdin)
  let result = checkDigit(number)
  echo result.input, result.check_digit

for_stmt.nim

echo "Counting to ten: "
for i in countup(1, 10):
  echo i

echo "Counting to 10: "
var i = 1
while i <= 10:
  echo i
  inc(i) # increment i by 1

echo "Counting down from 10 to 1: "
for i in countdown(10, 1):
  echo i

echo "Counting to 1..10: "
for i in 1..10:
  echo i

for index, item in ["a", "b"].pairs:
  echo item, " at index ", index

greetings.nim

# This is a comment
echo "What's your name? "

#[
  multi line comment!!
]#
let name = readLine(stdin)
case name
of "":
  echo "Poor soul, you lost your name?"
of "name":
  echo "Very funny, your name is name."
of "Dave", "Frank":
  echo "Cool name!"
else:
  echo "Hi, ", name, "!"

Makefile

.PHONY: build release

sources := greetings.nim number.nim while_stmt.nim for_stmt.nim when_stmt.nim block_stmt.nim stmt_and_indent.nim procedures.nim

build:
	$(foreach source, $(sources), $(shell nim compile $(source) > /dev/null))
	@echo "build finish"

release:
	$(foreach source, $(sources), $(shell nim c -d:release $(source) > /dev/null))
	@echo "release compile finish"

clean:
	rm -rf nimcache

number.nim

from strutils import parseInt

echo "A number please: "
let n = parseInt(readLine(stdin))
case n
of 0..2, 4..7: echo "The number is in the set: {0, 1, 2, 4, 5, 6, 7}"
of 3, 8: echo "The number is 3 or 8"
else: discard

procedures.nim

proc yes(question: string): bool =
  echo question, " (y/n)"
  while true:
    case readLine(stdin)
    of "y", "Y", "yes", "Yes": return true
    of "n", "N", "no", "No": return false
    else: echo "Please be clear: yes or no"

if yes("Should I delete all your important files?"):
  echo "I'm sorry Dave, I'm afraid I can't do that."
else:
  echo "I think you know what the problem is just as well as I do."

stmt_and_indent.nim

var x, y: bool

#[
x = true
y = true
]#

# no indentation needed for single assignment statement:
if x: x = false

# indentation needed for nested if statement:
if x:
  if y:
    y = false
  else:
    y = true

# indentation needed, because two statements follow the condition:
if x:
  x = false
  y = false

when_stmt.nim

when system.hostOS == "windows":
  echo "running on Windows!"
elif system.hostOS == "linux":
  echo "running on Linux!"
elif system.hostOS == "macosx":
  echo "running on Mac OS X!"
else:
  echo "unknown operating system"

while_stmt.nim

echo "What's your name? "
var name = readLine(stdin)
while name == "":
  echo "Please tell me your name: "
  name = readLine(stdin)