![]() ![]() When you want to check for a nil rather than catch an exception, there are method versions suffixed with a ? which provide that. And the combination of exceptions and type-safety does an excellent job of getting rid of most of the function return error checking I’d have to write in other languages. #Crystal programming language pdf code#The point of all of this is that you can create a web application as you might using Ruby on Rails, but you won’t have to spend as much time writing tests, because some of the most common problems of Ruby code are taken care of by the type system. Paul Smith of Thoughtbot (a company well-known for their Ruby on Rails expertise) is creating the Lucky web framework, written in Crystal and inspired by Rails, which has pervasive type-safety – and without the declaration overhead as in Java. And these are small issues compared to the benefits of the language. But Crystal already stores strings and some other data this way. I actually like it from an error-catching perspective, and to store some constant data in a way that’s easily shareable across multiple threads. ![]() The developers correctly point out that const is propagated through all of your code and doesn’t often result in code optimization. The developers complain that LLVM and LLDB have changed their debugging data format several times recently. ![]() What have I missed so far? Run-time debugging is at a very primitive state. There are pointers and structs, so systems programming (like device drivers) is possible. Pointers and cross-language calls are “unsafe” (can cause segmentation faults, buffer overflows, etc.) but most programmers would never go there. There is an excellent interface to cross-language calls, so you can incorporate C code, etc. Most of the methods of String are duplicated for macros, so you can do arbitrary textual transformations. You can call shell commands at compile-time and incorporate their output into macros. The macro system gives access to AST nodes in the compiler, type inference, and a very rich set of operators. And there is an extremely powerful macro system. Then there are generics which allow you to declare a class with parameterized types. Type inference and duck typing gives functions and class methods parameterized types for free, without any declaration overhead. So, if you want to see nil, you can declare your variable this way: a : String | NilĬrystal handles metaprogramming in several ways. So, this catches all of those problems you might have in Ruby or Javascript with nil popping up unexpectedly as a value and your code breaking in production because nil doesn’t have the methods you expect. If you declare the type of a variable, the compiler will complain at compile-time if anything tries to assign another type to it. Now, let’s say you never want to see nil as a variable value. Similarly, the type of a variable can be inferred from what you assign to it, and does not have to be declared. If a method isn’t available in a type, you’ll find out at compile-time. ![]() You get type-safe duck-typing at compile-time. So, if you write a function like this: def add(a, b)Īdd(1, 2) # => 3, and the returned type is Int32Īdd(1.0, 2) # => 3.0, and the returned type is Float64 It does this through program-wide type inference. #Crystal programming language pdf software#You really can program in a Ruby-like language and achieve software that performs with the speed of a compiled language.īut the greatest advantage of Crystal, that I have experienced so far, is that it provides type-safety without excessive declarations as you would see in Java. It has some compelling features that make it more attractive than other modern language attempts like Go. Crystal is a rising programming language with the slogan “Fast as C, Slick as Ruby”. ![]()
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