| HN Mirror

> C/Java style of annotating the return type of a function first, and then annotating the argument types before the name feels really old school at this point. Python, TypeScript, Go, Rust, etc. all opted for annotating after the name.

> Since this is so prevalent in newer languages, despite a pretty strong tradition in the other direction, I wonder if there is a pretty good reason for this which language design experts are keenly aware of when they design new languages.

My $0.02:

Maybe consistency between named functions and anonymous functions?

If you put the return type of a function before the name then it reads ambiguously when the name is left out (as in anonymous functions):

// Named function

int funcName (params) { ... }

// No-name function

int (params) { ... }

Which leads to the language needing alternative syntax or extra keywords when declaring anonymous functions:

// Something like this maybe?

int lambda (params) { ... }

If you put the return type after the function information but before the body then it's always consistent:

// Named function

funcName (params) : int { ... }

// No-name function

(params) : int { ... }

And, of course, to retain consistency you then make sure that all variables are declared the same way (type following variable name):

// Var declaration

myvar : int;

The disambiguation comes into its own when creating functions inline:

// Prefixed return-type looks odd

callFooWithFunc (int (argslist) { ... });

// Prefixed return-type requires extra keywords to not look odd

callFooWithFunc (int lambda (argslist) { ... });

// Suffixed return-type looks normal

callFooWithFunc ((argslist) : int { ... });