Basics

Basics #

Getting Started #

Installing Nim #

Please refer to the Install Nim Guide.

Compiling #

To compile a nim file in the most basic way (executable will have same name as the part before .nim):

nim c nimFileName.nim

You can automatically execute it after a compile by adding -r:

nim c -r nimFileName.nim

You can add a parameter to set the output folder and binary name:

nim c -o:pathToFolder/programExecutable nimFileName.nim

Indentation #

Nim uses indentation similar to Python, it uses two spaces instead of brackets or end like other languages:


if 42 == 42:
  echo "42 is equal to 42"

Assigning Variables #

Nim is a statically typed programming language, so a type needs to be declared before using the value:


var num: int = 44

Though the value can often be inferred, so it could also be declared this way:


var num = 44

You can also declare many variables at the same time:


var
  num1 = 42
  string1 = "it doesn't have to be the same type"
  char1 = 'c'

Unlike most languages you can use both snake case and camel case, they are interchangeable:


var
  snake_case_variable = "this is the same as snakeCaseVariable"
  camelCaseVariable = "this is the same as camel_case_variable"

If you need to use the same word as a reserved keyword, you can use stropping by adding backticks (`):


var `var` = "this is a stropped variable

Variables cannot begin with a number and cannot contain two consecutive underscores, it can also use Unicode characters.

var #

The var type declares a variable that can be changed (it is mutable):


var thisValueCanChange = 4
thisValueCanChange = 5

let #

The let type declares a variable that cannot change once it is set (it is immutable), but doesn’t have to be known at compile time:


let thisValueCannotChange = 42

const #

The const type declares a variable that cannot change (it is immutable) and is known at compile time:


const thisValueCannotChangeEither = 42

Export Symbol #

To allow a variable, procedure, object, etc to be exported to be accessed outside of a module you have to add an *:

var a*: int # this is available outside of the module

Comments #

Comments start with a #:

# this is a comment

Multiline comments are started with a #[ and ended with a ]#:

#[
This is a 
multiline comment
on a few lines.
  #[
    These comments
    can also
    be nested!
  ]#
]#

Document comments start with a ## and are used when generating documentation and are only generated if the types/procedures/etc are exported or public, as when using a *.

var number*: int = 44 ## number is used to store a number.

A discard statement can also be used with long string literals """ to create comments:

discard """This is just like
a multiline comment
but with the discard statement"""

Basic Data Types #

Integers #

Support for binary, octal, hexadecimal numbers comes built-in:


let
  num0: int = 79 # decimal number
  num1: int = 0x4F # hex number
  num2: int = 0b1001111 # binary number
  num3: int = 0o117 # octal number

There is also support for unsigned numbers:


let num0: uint = 79 # unsigned number

Numbers can be explicitly assigned a size by adding it after int or uint (8, 16, 32, 64):


let
  num8bit: int8 = -79
  num8bitunsigned: uint8 = 79

You can also use underscores to improve readability of numbers, Nim ignores them:

let 
  numWithUnderscores = 1_000_000
  numWithoutUnderscores = 1000000
echo numWithUnderscores == numWithoutUnderscores # prints true

Floats #

The fastest type for floats is float:


let floatNum: float = 42.0

Floats have two different suffixes based on their size and is preceded with a apostrophe (') and the size ( 'f32 for float32 and 'f64 for float64):


let
  floatNum32: float = 44'f32
  floatNum64: float = 44'f64

Characters #

The char type is for representing a single ASCII character and is wrapped with two single apostrophes ('):


let
  zed: char = 'z'
  two: char = '2'
  pound: char = '#'

Special Characters #

  • \n is a newline character
  • \t is a tab character
  • \\ is a backslash (since the first \ is an escape character)
  • r"..." is for raw strings to output an exact string ignoring special characters in the quotes

echo "This has a newline at the end.\n"
echo "This has a \t tab in the sentence."
echo "This has a \\ backslash in the sentence."
echo r"This has\n no special characters\n at all."

Strings #

Strings are best explained as a series of characters and is wrapped around two double quotes ("), these are all valid:


let
  a: string = "cool"
  b: string = "This is an example sentence."
  c: string = ""
  d: string = "42"
  e: string = "@"

Booleans #

A boolean type can only have two values, true or false.


let
  trueVariable: bool = true
  falseVariable: bool = false

Basic Operations #

Arithmetic #

The following math operators are in Nim: +, -, *, and /.

The / operator will always give a floating point number as a result even if no remainders exist:


10/5 # results in 2.0

In a similar manner, when doing any arithmetic with floating point numbers, a float will result even if no remainders or decimals result:


4.25 - 2.25 # results in 2.0
2.0/2.0 # results in 1.0

The precedence of math operation is as expected, with multiplying and dividing having a higher priority than addition/subtraction.

Integer division is possible by using div operator to discard the remainder:


5 div 4 # results in 1

To get the remainder only, the modulus operator, mod can be used:


10 mod 4 # results in 2

These two operators will always result in integers.

Comparison #

Nim provides <,>, ==, != boolean operators. These support numbers, characters, and strings:


5 < 4 # false
5 == 5 # true
4.4 < 55.5 # true
'c' < 'd' # true
'c' != 'c' # false
"first" < "second" # true

Character/String comparison rules:

  • All uppercase letters come before lowercase letters.
  • When comparing strings, it is char-by-char, the letters that come first are smaller than characters later in the alphabet.
  • A shorter string is considered smaller than a longer one.

There are also logical operators and, or, xor, and not.

  • The and operator returns true only if both members are true.
  • The or operator returns true if at least one member is true.
  • The xor operator returns true if one member is true, but the other is not.
  • The not operator negates the boolean value to the opposite value and only takes one argument.

true and true # is true
true and false # is false
false and false # is false

true or true # is true
true or false # is true
false or false # is false

true xor true # is false
true xor false # is true
false xor false # is false

not true # is false
not false # is true

String Concatenation #

As long as you use var to define the string, we can use add to add another string to the string variable:


var a = "test strings are "
a.add("for testing")
echo a # outputs "test strings are for testing"

We can also combine the two to echo to the screen using two ways:


var a = "test strings are "
echo a & "for testing" # outputs "test strings are for testing"
echo a, "for testing" # outputs "test strings are for testing"

We also can use & to combine strings into a variable declaration:


var 
  a = "test strings are "
  b = "for testing"
  c = a & b
  d = a, b # this won't compile

Type Conversion #

Adding a $ to a variable name makes it into a string:


var 
  number: int = 44
  itsAString: string = $number

Convert a float to an int (it does not round the number, but just drops any decimals):


let a = 4.0
echo int(a)

Convert an int to a float:


let b = 4
echo float(b)