nim-wiki/Nimrod-for-C-programmers.md

(Work in progress)

This is a guide for people with experience in C or a similar language. The general tutorials can be found here:

http://nimrod-lang.org/tut1.html
http://nimrod-lang.org/tut2.html

The manual provides a more or less complete overview of the language:

http://nimrod-lang.org/manual.html

At a glance

Feature	C	Nimrod
Memory Management	Manual (not counting libraries)	Garbage-collected and manual
Types	Static	Static
Compilation	Machine code	Machine code via C (other backends in progress/planned)
Meta-programming	C Preprocessor	Nimrod (const/when/template/macro)

### Structs - Tuples and Objects

Tuples and Objects in Nimrod are kind of like structs in C, but not really.

Interfacing C and Nimrod

See Foreign Function Interface

Converting C code to Nimrod

See c2nim

Cheat Sheet

Note: Code examples are not exactly one-to-one, there may be subtle differences in the semantics. See comments.

C	Nimrod	Comment
```C int x; int y = 2; ```	```Nimrod var x : int var y1 : int = 2 var y2 = 2 let z = 2 ```	Define variable. y2 uses type inference. z is single-assignment. In nimrod, uninitialized variables is initialized to 0/nil or similar defaults.
```C 9 % 8 // 1 -9 % 8 // -1 (unsigned)(-9) % (unsigned)(8) // 7 ```	```Nimrod 9 mod 8 # 1 -9 mod 8 # -1 -9 %% 8 # 7 ```	Modulo operator. %% treats its argument as unsigned numbers. See
```C int x = foobar() ? 42 : 0; ```	```Nimrod var x = if foobar(): 42 else: 0 ```	If-statements return the value of the expression they evaluate to, so Nimrod doesn't need a ternary operator.
```C void foo() { printf("Hello World\n"); } int bar() { return 2; } int baz(int x) { return x*2; } ```	```Nimrod proc foo() = echo "Hello World" proc bar() : int = 2 proc baz(x : int) = x*2 </td> <td><b>Function/Procedure.</b> </td> </tr> <tr> <td> ```C void foobar(person_t *a) { person_t b; b = *a; b.name = "Bob"; *a = b; }	```Nimrod proc foobar(a: ref TPerson) = var b: TPerson b = a[] b.name = "Bob" a[] = b ```	Dereference. In C, only the pointer to the strings in the struct is copied. In Nimrod, the string is also copied, but refs are not deep-copied.