Ada: a C Developer's Perspective

Post by flukus » Thu, Apr 27, 2017, 10:50 AM UTC

pavlov wrote: post #8

flukus wrote: post #4

So how does Ada go speed wise (real world not micro benchmarks)? Were/are there legitimate reasons to opt for c over Ada?

On early PCs, Pascal and C were pretty much tied in popularity. Both were free to implement, and small enough that you could make a fast compiler on a typical PC with only 256-640 kB RAM. C won because it was more flexible and was chosen by Microsoft, but Pascal definitely had a strong following (it was the original Mac's API language, and on PC it was a major contender thanks to the nice and fast Turbo Pascal IDE).…

Post by ewanm89 » Thu, Apr 27, 2017, 10:53 AM UTC

JohnStrange wrote: post #68

ewanm89 wrote: post #35

Here is my list of shortcomings when it comes to Ada 1) Ada is not a magic bullet, the seminal case study of why computer bugs are bad taught in CS courses around the world is the failed 1996 Ariane 5 rocket launch where the rocket veered off course and then exploded due to a software error that caused it not to understand the data it was getting from a sensor. More recently there are plenty of demonstrations of poor…

I feel like I have to rule out some misconceptions and defend Ada a bit, even though I don't use it very often any longer. Ada is not a magic bullet 1) Nothing is a magic bullet. (And certainly no actual user of Ada has ever claimed that it is a magic bullet.) Ada is not easy to write, it's around the level of C I grant you. 2) Ada is way harder to write than C, unless you're very proficient with it, of course. It's…

Post by wBI8j2bsb » Thu, Apr 27, 2017, 10:56 AM UTC

dbrgn wrote: post #50

krylon wrote: post #29

Earlier quoted context omitted.

> The subtyping feature I love the most. I only have very little experience with Ada, but being able to define a type whose values are integers in the range, say, 1 .. 7, to represent days of a week was an eye opener.

Range types are probably the main thing I miss from the Rust type system. But even without range constraints, wrapper types (called newtypes in Haskell and Rust) are great. Let's say you have a function that accepts a temperature. A temperature is a float, but you want to prevent the user from mixing up celsius and fahrenheit. This is what newtype looks like in Rust: struct Celsius(pub f64); struct Fahrenheit(pub f64…

  #include 

  typedef struct { double v; } Celsius;
  typedef struct { double v; } Fahrenheit;

  void
  print_celsius(Celsius temperature) {
      printf("Temperature is %f", temperature.v);
  }

  void
  compile_error(Fahrenheit temperature)
  {
      print_celsius(temperature);
  }

Post by Raphael_Amiard » Thu, Apr 27, 2017, 11:17 AM UTC

flukus wrote: post #75

Raphael_Amiard wrote: post #67

Earlier quoted context omitted.

In theory, it's just as fast as C/C++, when you compare GNAT against GCC/G++. In practice, some language constructs are not as optimized as their C++ counterpart. The end result is that you can expect the Ada 83 subset to be extremely fast, but more recent constructs like OO and controlled types (equivalent to C++ virtual destructors) to be slower. All in all it has a pretty good performance story !

> In theory, it's just as fast as C/C++, when you compare GNAT against GCC/G++. Is this the same theory that makes java is just as fast? Ie, if I wrote idiomatic Ada would the levels of indirection (pointers to pointers to pointers and virtual functions everywhere) by more like c or more like java?

Post by [deleted] » Thu, Apr 27, 2017, 12:00 PM UTC

wBI8j2bsb wrote: post #76

dbrgn wrote: post #50

Earlier quoted context omitted.

Range types are probably the main thing I miss from the Rust type system. But even without range constraints, wrapper types (called newtypes in Haskell and Rust) are great. Let's say you have a function that accepts a temperature. A temperature is a float, but you want to prevent the user from mixing up celsius and fahrenheit. This is what newtype looks like in Rust: struct Celsius(pub f64); struct Fahrenheit(pub f64…

This is exactly what C does. #include typedef struct { double v; } Celsius; typedef struct { double v; } Fahrenheit; void print_celsius(Celsius temperature) { printf("Temperature is %f", temperature.v); } void compile_error(Fahrenheit temperature) { print_celsius(temperature); } I suspect LLVM will clean this up to plain floats as well.