summaryrefslogtreecommitdiffhomepage
path: root/nim.html.markdown
blob: e3c749dc5329db81802da038bb1a30bc7b63a1f9 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
---
language: Nim
filename: learnNim.nim
contributors:
    - ["Jason J. Ayala P.", "http://JasonAyala.com"]
    - ["Dennis Felsing", "https://dennis.felsing.org"]
---

Nim (formerly Nimrod) is a statically typed, imperative programming language
that gives the programmer power without compromises on runtime efficiency.

Nim is efficient, expressive, and elegant.

```nim
# Single-line comments start with a #

#[
  This is a multiline comment.
  In Nim, multiline comments can be nested, beginning with #[
  ... and ending with ]#
]#

discard """
This can also work as a multiline comment.
Or for unparsable, broken code
"""

var                     # Declare (and assign) variables,
  letter: char = 'n'    # with or without type annotations
  lang = "N" & "im"
  nLength: int = len(lang)
  boat: float
  truth: bool = false

let            # Use let to declare and bind variables *once*.
  legs = 400   # legs is immutable.
  arms = 2_000 # _ are ignored and are useful for long numbers.
  aboutPi = 3.15

const            # Constants are computed at compile time. This provides
  debug = true   # performance and is useful in compile time expressions.
  compileBadCode = false

when compileBadCode:            # `when` is a compile time `if`
  legs = legs + 1               # This error will never be compiled.
  const input = readline(stdin) # Const values must be known at compile time.

discard 1 > 2 # Note: The compiler will complain if the result of an expression
              # is unused. `discard` bypasses this.


#
# Data Structures
#

# Tuples

var
  child: tuple[name: string, age: int]   # Tuples have *both* field names
  today: tuple[sun: string, temp: float] # *and* order.

child = (name: "Rudiger", age: 2) # Assign all at once with literal ()
today.sun = "Overcast"            # or individual fields.
today.temp = 70.1

# Sequences

var
  drinks: seq[string]

drinks = @["Water", "Juice", "Chocolate"] # @[V1,..,Vn] is the sequence literal

drinks.add("Milk")

if "Milk" in drinks:
  echo "We have Milk and ", drinks.len - 1, " other drinks"

let myDrink = drinks[2]

#
# Defining Types
#

# Defining your own types puts the compiler to work for you. It's what makes
# static typing powerful and useful.

type
  Name = string # A type alias gives you a new type that is interchangeable
  Age = int     # with the old type but is more descriptive.
  Person = tuple[name: Name, age: Age] # Define data structures too.
  AnotherSyntax = tuple
    fieldOne: string
    secondField: int

var
  john: Person = (name: "John B.", age: 17)
  newage: int = 18 # It would be better to use Age than int

john.age = newage # But still works because int and Age are synonyms

type
  Cash = distinct int    # `distinct` makes a new type incompatible with its
  Desc = distinct string # base type.

var
  money: Cash = 100.Cash # `.Cash` converts the int to our type
  description: Desc  = "Interesting".Desc

when compileBadCode:
  john.age  = money        # Error! age is of type int and money is Cash
  john.name = description  # Compiler says: "No way!"

#
# More Types and Data Structures
#

# Enumerations allow a type to have one of a limited number of values

type
  Color = enum cRed, cBlue, cGreen
  Direction = enum # Alternative formatting
    dNorth
    dWest
    dEast
    dSouth
var
  orient = dNorth # `orient` is of type Direction, with the value `dNorth`
  pixel = cGreen # `pixel` is of type Color, with the value `cGreen`

discard dNorth > dEast # Enums are usually an "ordinal" type

# Subranges specify a limited valid range

type
  DieFaces = range[1..20] # Only an int from 1 to 20 is a valid value
var
  my_roll: DieFaces = 13

when compileBadCode:
  my_roll = 23 # Error!

# Arrays

type
  RollCounter = array[DieFaces, int]  # Arrays are fixed length and
  DirNames = array[Direction, string] # indexed by any ordinal type.
  Truths = array[42..44, bool]
var
  counter: RollCounter
  directions: DirNames
  possible: Truths

possible = [false, false, false] # Literal arrays are created with [V1,..,Vn]
possible[42] = true

directions[dNorth] = "Ahh. The Great White North!"
directions[dWest] = "No, don't go there."

my_roll = 13
counter[my_roll] += 1
counter[my_roll] += 1

var anotherArray = ["Default index", "starts at", "0"]

# More data structures are available, including tables, sets, lists, queues,
# and crit bit trees.
# http://nim-lang.org/docs/lib.html#collections-and-algorithms

#
# IO and Control Flow
#

# `case`, `readLine()`

echo "Read any good books lately?"
case readLine(stdin)
of "no", "No":
  echo "Go to your local library."
of "yes", "Yes":
  echo "Carry on, then."
else:
  echo "That's great; I assume."

# `while`, `if`, `continue`, `break`

import strutils as str # http://nim-lang.org/docs/strutils.html
echo "I'm thinking of a number between 41 and 43. Guess which!"
let number: int = 42
var
  raw_guess: string
  guess: int # Variables in Nim are always initialized with a zero value
while guess != number:
  raw_guess = readLine(stdin)
  if raw_guess == "": continue # Skip this iteration
  guess = str.parseInt(raw_guess)
  if guess == 1001:
    echo("AAAAAAGGG!")
    break
  elif guess > number:
    echo("Nope. Too high.")
  elif guess < number:
    echo(guess, " is too low")
  else:
    echo("Yeeeeeehaw!")

#
# Iteration
#

for i, elem in ["Yes", "No", "Maybe so"]: # Or just `for elem in`
  echo(elem, " is at index: ", i)

for k, v in items(@[(person: "You", power: 100), (person: "Me", power: 9000)]):
  echo v

let myString = """
an <example>
`string` to
play with
""" # Multiline raw string

for line in splitLines(myString):
  echo(line)

for i, c in myString:       # Index and letter. Or `for j in` for just letter
  if i mod 2 == 0: continue # Compact `if` form
  elif c == 'X': break
  else: echo(c)

#
# Procedures
#

type Answer = enum aYes, aNo

proc ask(question: string): Answer =
  echo(question, " (y/n)")
  while true:
    case readLine(stdin)
    of "y", "Y", "yes", "Yes":
      return Answer.aYes  # Enums can be qualified
    of "n", "N", "no", "No":
      return Answer.aNo
    else: echo("Please be clear: yes or no")

proc addSugar(amount: int = 2) = # Default amount is 2, returns nothing
  assert(amount > 0 and amount < 9000, "Crazy Sugar")
  for a in 1..amount:
    echo(a, " sugar...")

case ask("Would you like sugar in your tea?")
of aYes:
  addSugar(3)
of aNo:
  echo "Oh do take a little!"
  addSugar()
# No need for an `else` here. Only `yes` and `no` are possible.

#
# FFI
#

# Because Nim compiles to C, FFI is easy:

proc strcmp(a, b: cstring): cint {.importc: "strcmp", nodecl.}

let cmp = strcmp("C?", "Easy!")
```

Additionally, Nim separates itself from its peers with metaprogramming,
performance, and compile-time features.

## Further Reading

* [Home Page](http://nim-lang.org)
* [Download](http://nim-lang.org/download.html)
* [Community](http://nim-lang.org/community.html)
* [FAQ](http://nim-lang.org/question.html)
* [Documentation](http://nim-lang.org/documentation.html)
* [Manual](http://nim-lang.org/docs/manual.html)
* [Standard Library](http://nim-lang.org/docs/lib.html)
* [Rosetta Code](http://rosettacode.org/wiki/Category:Nim)