Objective-C vs ATS
When comparing Objective-C vs ATS, the Slant community recommends ATS for most people. In the question“What are the best (productivity-enhancing, well-designed, and concise, rather than just popular or time-tested) programming languages?” ATS is ranked 49th while Objective-C is ranked 62nd. The most important reason people chose ATS is:
ATS has a theorem-proving type system powerful enough to prove that its functions meet their specifications. This happens at compile time with no performance impact at runtime. This can be used to prove that an ATS program doesn't have bugs commonly found in C++ programs, like "this function never leaks memory" or "this program never attempts to divide by zero" or "this buffer never overflows" or to verify pointer arithmetic, etc.
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Pros
Pro Well Documented
Objective-C's documentation exists on Apple's website, and explains language features in detail.
Pro Develop Apple applications
Similar to C# and Java, but used to develop native applications for Apple hardware.
Pro Objective-C supports an open style of dynamic binding
A style that can accommodate a simple architecture for interactive user interfaces.
Pro Built-in formal specification
ATS has a theorem-proving type system powerful enough to prove that its functions meet their specifications. This happens at compile time with no performance impact at runtime. This can be used to prove that an ATS program doesn't have bugs commonly found in C++ programs, like "this function never leaks memory" or "this program never attempts to divide by zero" or "this buffer never overflows" or to verify pointer arithmetic, etc.
Pro Free and open-source compiler
The compiler (ATS/Postiats) is GPLv3.
Pro Functional programming
The syntax is ML-like with the usual functional language features like pattern matching and tail-call optimization.
Pro High-performance systems language
ATS works as a low-level systems language. ATS programs have performance and footprint comparable to programs written in C/C++.
Pro Good module system
Similar to Modula-3. This makes ATS a viable choice even for large-scale projects.
Pro Safe concurrency
ATS can prove its concurrent programs have no deadlocks or race conditions.
Cons
Con Odd Syntax
Objective C's syntax is very alien to other languages. Learning Objective-C first will fail to expose you to a syntax style that would be relatively familiar in almost any other language.
Con Might as well learn Swift
Swift works almost anywhere Objective C does, and it was designed to replace Objective C.
Con One of the biggest mistakes ever.
It was meant to be one of the C-style languages, but has such bad syntax design it actually is the odd duck.
Con Apple-centric and obsolete
Con Tied into Apple's eco-system.
Con More Technical
To be able to do basic tasks in Objective-C requires a strong understanding of programming.
Con Requires Understanding of C-language.
Objective-C is built on top of C, and as such, requires at least a basic understanding of how to program in C.
Con No Windows version
But it does run on Cygwin.