Szathmáry László honlapja @ DEIK | Nim2 / Default values of variables

When you declare a variable in C and do not initialize it, it'll have a garbage value.

(1) C code

#include <stdio.h>

int main()
{
int x;

printf("x: %d\n", x); // -73847465, i.e. garbage value

return 0;
}

Nim, on the other hand, implicitly initializes every declared variable if you do not assign a value to it. The memory location of a primitive variable will be filled with zeroes.

When you declare a string, it'll be an empty string (and not a nil).

(2) Nim code

import std/strformat # &"Hello {name}!"

var
a: int # 0
b: bool # false
c: char # '\0'
d: float # 0.0
s: string # ""

echo "a: ", a
echo "b: ", b
echo &"c: '{c}'; ASCII code: {ord(c)}"
echo "d: ", d
echo &"s: '{s}'; length: {len(s)}"

Output:

a: 0
b: false
c: '�'; ASCII code: 0
d: 0.0
s: ''; length: 0

Tip

However, explicit is better than implicit. When you need a counter, I think it's a good practice to explicitly set its value to 0, to avoid confusion:

# var counter: int # it would also work since its initial value would be 0
var counter = 0 # explicit, easier to read

for i in 1..5: # executed 5 times
counter += 1

echo counter # 5