SOL: Simple Obvious Language

Sol is an imperative, statically-typed language designed as a tool for learning how to program. It is simple, in that it has few language features and can thus be learned quickly. It is obvious, in that it should be clear from reading the source code of an application what instructions the computer will execute.

Many common programming language features that allow programs to be more expressive were intentionally left out. See non-features for more details.

Examples

Hello, world!

function main() {
  print("Hello, world!");
}

Explicit Type Casts

function main() {
  constant answer = 42;
  constant message = "The secret is " + String(42);
  print(message);
}

Max Number

function maxNumber(numbers Number[]) -> Number {
  variable max = 0;
  for index, number in numbers {
    if index == 0 {
      max = number;
      continue;
    }
    if number > max {
      max = number;
    }
  }
  return max;
}

function main() {
  variable allNumbers = Number[1, 7, 3];
  variable bigNumber = maxNumber(allNumbers);
  print("The biggest number is " + String(bigNumber)); # The biggest number is 7
}

Recursion

function fibonacci(num Number) -> Number {
  if (n <= 1) {
    return n;
  }
  return fibonacci(n - 1) + fibonacci(n - 2);
}

Non-features

What should be of more note to existing programmers is not what features Sol implements, but rather those it does not. What follows is a non-comprehensive list, along with the rationale for omitting it.

Mutable Global State

While Sol allows constants to be defined globally, it does not have global variables. Variables only exist within the scope of a function, and to share them you must either pass their value or a pointer to them via function arguments.

Sol Syntax

Keywords

Keyword	Description	Implemented?
variable	A mutable variable	[x]
constant	An immutable variable	[ ]
function	A custom function.	[x]

Primitives

Type	Example	Description	Implemented?
String	"Hello, world!"	ASCII, immutable string	[x]
Number	12.3	Floating point number (currently 32-bit)	[x]
boolean	variable shouldUpdate = false;	Either true or false	[x]

Composite Types

Type	Example	Description	Implemented?
List	String["A", "b", "Hello, world!"]	An untyped, growable list of objects	[x]
Map	Number{"age": 36}	Hash map from String to a single type.	[ ]

Control Flow

Keyword	Example	Implemented?
if	if check() {}	[x]
for & in	for idx, el in elementList {}	[x]

Standard Library

Process

Function Name	Description	Implemented?
run(String[])	Run a subprocess.	[x]

I/O

Function Name	Description	Implemented?
print(String)	Print a String to STDOUT	[x]
printError(String)	Print a String to STDERR	[ ]