Ada

Ada was designed for the United States Department of Defense by a team led by Jean Ichbiah, and its first reference manual appeared in 1980. It’s named after Ada Lovelace, who wrote what is often called the first computer program. Ada was built for large programs that must not fail, and it still flies in aircraft, runs railway signals, and guides air traffic control. GNAT, the compiler used here, is part of GCC.

Ada spells things out. Blocks end with end if, end loop, and end Main, and every value has a type that the compiler checks strictly. It won’t mix integers and floats, or even two integer types, without a conversion. Arrays can be indexed from any range you choose, and they carry their bounds with them as A'First and A'Last. Containers and sorting are generics: you make a copy for your own types with is new. Crates from Alire, Ada’s package manager, aren’t installed here. The run script turns on most of GNAT’s warnings with -gnatwa and makes each one an error.

Quirks

• X / Y with an Integer X and a Float Y doesn’t compile (“invalid operand types for operator”). You convert first: Float (X) / Y.
• Integer / rounds toward zero, so (-7) / 2 is −3. Ada has both mod and rem, which differ on negative numbers: (-7) mod 3 is 2, and (-7) rem 3 is −1.
• Write (-7) / 2, not -7 / 2: GNAT warns that the unary minus should be parenthesized, and here that warning stops the build.
• Integer overflow is checked. Adding 1 past Integer'Last raises CONSTRAINT_ERROR : overflow check failed instead of wrapping around.
• Integer'Image (5) is " 5", with a space where a minus sign would go. Long_Float'Image (2.0 / 3.0) gives 6.66666666666667E-01, so the programs print with Put and Exp => 0 instead.
• An array literal is written with square brackets, [3, 1, 2]. The older round brackets still work, but GNAT warns that they’re obsolescent.
• Ada.Text_IO and Ada.Strings.Fixed both have a Count, so with both in use, a bare Count (Line, ",") doesn’t compile until you name the package: Ada.Strings.Fixed.Count.
• An enumeration value prints in capitals: with type Feature is (Has_Link, Known_Sender), Feature'Image (Has_Link) is "HAS_LINK".

git clone https://github.com/qnixon/dswithx.git
cd dswithx
python3 harness/run_tests.py --language ada