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AQA++

AQA++ is an unofficial implementation of the AQA psuedocode specification in Go. It also supports some features that aren't in the spec (such as maps) in order to make it slightly more usable, hence the ++ in the name. It is interpreted and the design of the interpreter is based on the one described in the book Writing An Interpreter in Go.

Demo

For now, if you want to try it out, you can go to https://aqa.ollybr.repl.run/ for a REPL and https://repl.it/@ollybr/AQA if you want to write a file. Both of those are just REPL.ITs that download the executable from my website and run it.

For more examples, see the _examples folder.

Syntax

Specification

Everything in the AQA specification. One big difference is that there is no support for special characters at the moment. In the spec, it uses unicode characters such as ← for assignment and ≥ for greater than or equal. In this version, only the ascii equivalents are supported.

Specification Equivalent Purpose
← <- Assignment: a <- 10
≥ >= Greater than or equal: 10 >= 20 # false
≤ <= Less than or equal: 10 <= 20 # true
≠ != Not equal to: 10 != 20 # true

Additions

Additions to the spec (hence to ++)

  • Everything doesn't need to be uppercase:

    a <- STRING_TO_INT("5")
a <- string_to_int("5")

  • Easily define hexadecimal and binary numbers:

    hex <- 0x1A4 # 420
bin <- 0b101010 # 42

  • Many more builtin functions, such as SQRT, FLOOR and EXIT.

    a <- sqrt(8)
a - 2*sqrt(2) == 0 # True

EXIT(1) # Exits the program with 1 as exit code

  • Bitshifts using >> and <<

    bin <- 0b0001
bin << 3 # 0b1000 or 8

  • Type Coercion

    fav_num <- 5
OUTPUT "Your favourite number is: " + fav_num

# No need to convert to string.

  • Maps: using the { syntax }

    a <- MAP {
  "hello": true,
  "goodbye": false,
  [1,2]: "foo"
}

Also, it WILL support the following (to be added)

  • FN: A function definition that is an expression. Like Python's lambda.

    See the map.aqa example. add_5 has to be defined seperately before use. In Python we could do

    print( map([1,2,3,4,5], lambda x: x + 5) )

    This would allow the following;

    OUTPUT map([1,2,3,4,5], FN(x) { x + 5 } )

  • More meaningful error messages

    "hello " + 5
# Current output: "ERROR: type mismatch: STRING + INTEGER"

"hello " + 5
# Something like
# error: addition not supported for `string` and `integer` on line 5:
#        "hello " + 5
# did you mean: "hello " + string(5)

Todo

  • More tests
  • Better type conversion system
  • Add support for unicode
  • Compile the project to WebAssembly so that it can be run in the browser without https://repl.it
  • Write a wiki/tutorial for the language
  • The module/import system is still very buggy, such as referencing variables defined in one file when those variables are not imported. Fix this.