Haste vs Nim

Haste was designed to allow both the client and server to be written as parts of the same, type-safe application. This is in stark contrast to most other options, where the client and server are considered two separate entities, resulting in extra manual validation code and more chances for type errors.

Haste supports the Haskell 2010 standard except for Template Haskell as well as most GHC extensions.

Haste lets you write client and server as a single program, automatically generating code for the server as well as the client, giving you full type safety even across the Internet.

There are generics, templates, macros in Nim. They can allow you to write new DSL for your application, or avoid all boilerplate stuff.

Checks your code at compile time.

With built-in "unittest" module you can create test with a very readable code.

Nim has "asyncdispatch" module, which allows you to write async applications.

Nim has a built-in VM, which executes macros and some other code at compile time. For example, you can check if you're on Windows, and Nim will generate code only for it.

The same code can be used for web, server, desktop and mobile.

Nim has a lot of common with Python in terms of syntax. Indentation-based syntax, for/while loops.

Imperative, OOP, functional programming in one language.

You can use Nim with any language that can be interfaced with C. There's a tool which helps you to create new C and C++ bindings for Nim - c2nim.
Also, you can use Nim with Objective C or even JavaScript (if you're compiling for these backends).

You don't need to deal with all those manual memory allocations, Nim can take care of it. But also you can use another GC, or tweak it for your real-time application or a game.

You only need to specify types in your procedures and objects - you don't need to specify type when you're creating a new variable (unless you're creating it without initialization).

You can use unicode names for variables, there is "unicode" module for operations with unicode.

writeLine(stdout, "hello") can be written as stdout.writeLine("hello")
proc add(a: int): int = a + 5 can be used like 6.add.echo or 6.add().echo()