Fabulous Adventures In Coding
Eric Lippert is a principal developer on the C# compiler team. Learn more about Eric.
Presented as a dialogue, as is my wont!
Is C# a strongly typed or a weakly typed language?
That is unhelpful.
I don't doubt it. Interestingly, if you rephrased the question as an "and" question, the answer would be the same.
What? You mean, is C# a strongly typed and a weakly typed language?
Yes, C# is a strongly typed language and a weakly typed language.
Me too. Perhaps you should tell me precisely what you mean by "strongly typed" and "weakly typed".
Um. I don't actually know what I mean by those terms, so perhaps that is the question I should be asking. What does it really mean for a language to be "weakly typed" or "strongly typed"?
"Weakly typed" means "this language uses a type verification system that I find distasteful", and "strongly typed" means "this language uses a type system that I find attractive".
These terms are meaningless and you should avoid them. Wikipedia lists eleven different meanings for "strongly typed", several of which contradict each other. Any time two people use "strongly typed" or "weakly typed" in a conversation about programming languages, odds are good that they have two subtly or grossly different meanings in their heads for those terms, and are therefore automatically talking past each other.
But surely they mean something other than "unattractive" or "attractive"!
I do exaggerate somewhat for comedic effect. So lets say: a more-strongly-typed language is one that has some restriction in its type system that a more-weakly-typed language it is being compared to lacks. That's all you can really say without more context.
How can I have sensible conversations about languages and their type systems then?
You can provide the missing context. Instead of using "strongly typed" and "weakly typed", actually describe the restriction you mean. For example, C# is for the most part a statically typed language, because the compiler determines facts about the types of every expression. C# is for the most part a type safe language because it prevents values of one static type from being stored in variables of an incompatible type (and other similar type errors). And C# is for the most part a memory safe language because it prevents accidental access to bad memory.
Thus, someone who thinks that "strongly typed" means "the language encourages static typing, type safety and memory safety in the vast majority of normal programs" would classify C# as a "strongly typed" language. C# is certainly more strongly typed than languages that do not have these restrictions in their type systems.
But here's the thing: because C# is a pragmatic language there is a way to override all three of those safety systems. Cast operators and "dynamic" in C# 4 override compile-time type checking and replace it with runtime type checking, and "unsafe" blocks allow you to turn off type safety and memory safety should you need to. Someone who thinks that "strongly typed" means "the language absolutely positively guarantees static typing, type safety and memory safety under all circumstances" would quite rightly classify C# as "weakly typed". C# is not as strongly typed as languages that do enforce these restrictions all the time.
So which is it, strong or weak? It is impossible to say because it depends on the point of view of the speaker, it depends on what they are comparing it to, and it depends on their attitude towards various language features. It's therefore best to simply avoid these terms altogether, and speak more precisely about type system features.
c# i think is a weakly typed language i.e it will find some loophole to do some implicit type conversion for nearly matching types' input arguments.
Excellent post,Nice and subtle approach to define what makes C# strongly typed
@Jimmy: In C#, 5 + "foo" does not imply a conversion to string. The operator+(object,string) is invoked. When compiled, you'll get a call to string.Concat(object,object). Still no conversion to string. In either case (operator+ or string.Concat), the arguments don't need to be converted to string.
Was wondering what your thoughts were on this article?
It's hard to call C# strongly typed when you can do things like the following:
uint i = unchecked((uint)-1);
[StructLayout(LayoutKind.Explicit)] struct SomeStruct
[FieldOffset(0)] float SomeFloat;
[FieldOffset(0)] byte SomeByte;
ulong SomeFunc(ulong i)
fixed (ulong* p = i) return (ulong)Interlocked.Read(*(long*)p); // there is no ulong overload for this
Among many other techniques to read data as a type that it clearly is not.
the "Weakly Typed Languages" article at
and the "Strong Typing" one at
(parts of the "Type Systems Demystified" series at
attempt to explain the differences between weak and strong typing by comparing the type systems of Perl,C# and VB.NET and how C#'s dynamic type changes the game (especially in the "C# Perl-like behavior?" section). Although very educational (I hope),the point of the articles is to show that in the end "These terms are meaningless and you should avoid them" as you have already pointed out