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Singlang v2: Now Uncle also can code

Why leh

Last time Uncle Seng tell ang moh friend that he want go work at the Face Book la. He say no more money liao, every week play 4D but always choose wrong one. He say if he go America there and make money by writing codes, can come back and play more 4D. Huat ah!

But ang moh tell Uncle Seng that his England sibei cui one, sure cannot make it through the "coding interview". Wah, then Uncle Seng super angry. He say then he dunnid the C++ la, Java la, he say if Singaporean can make Singlish, limpeh can make Singlang.

Simi Singlang?

Singlang:

ok uncle tell you story ah...

confirm plus chop x is 5
chope y as 1

x is 5 meh?
    ok den chope y as 6
    alamak den chope y as 7
ok can liao

chope i as 0
wait long long, i is 5 meh?
    chope i as i + 1
ok can liao

simi i

simi "Say something leh: "
chope u_say as "Simulated user input"
simi "ok u say: "
simi u_say

-- Dis one uncle's comment

ok uncle finish liao

But last time ang moh say one:

const x = 5;
let y = 1;

if (x == 5) {
    y = 6;
} else {
    y = 7;
}

let i = 0;

while (x != 5) {
    i = i + 1;
}

console.log(i);

console.log("Enter something: ");
let your_input = readLine();
console.log("What you typed: ");
console.log(your_input);

// This is a comment

Uncle i still dun understand

OK la uncle show you.

Must tell story

If u wan write Singlang codes, need start with

ok uncle tell you story ah...

then u end with

ok uncle finish liao

The Key Words liddat

Ang Moh Singlang
if / boolean test meh?
then ok den
else alamak den
end block ok can liao
var chope
const confirm plus chop
= (assignment) as (e.g. chope x as 5) / is (e.g. confirm plus chop x is 5)
while wait long long
print simi
read line makan
// for comments --

Den the Operators liddat

Must use meh? hor.

Operator Use
is Equality: x is 5 meh?
> More than: x > 5 meh?
< Less than: x < 5 meh?
>= More than or equal to: x >= 5 meh?
<= Less than or equal to: x <= 5 meh?
not Not equal to: x not 5 meh?

Uncle I want to try!

OK Uncle tell you how.

  1. You go install stack (https://docs.haskellstack.org/en/stable/README/), den learn how to use the "command line" abit abit .
  2. Clone this repository (top right got big green button one).
  3. Go the command line den run the stack build.
  4. Run stack install alex and stack install happy
  5. You faster test by running stack exec singlang-exe test-basic.lah - liddat the "interpreter" run the codes inside test-basic.lah.

Uncle I want more Singlang!

Ok can liao.

How to help you Uncle?

You go the "issues" there and tell Uncle what to put into Singlang.

Uncle explain abit

Click to expand

Actually, Uncle get his ang moh friend to explain abit.

Defining the Language

The entire language is defined in two files: res/Lexer.x and res/Parser.y. Note that Singlang is a completely defined language on its own, and is not doing string replacement followed by running another language's interpreter. This is to allow for unique syntax and semantics moving forward.

Lexer

Lexer.x defines the tokens in the language and what Haskell constructs they map to.

For example, digits in the language are defined as:

  $digit+				{ \s -> TInt (read s) }

Correspondingly, the data definition for the Token type has a definition for TInt Int. These two constructs define the tokenization for a particular token type.

To autogenerate the actual Lexer.hs file from Lexer.x, use the run_alex.sh script provided.

Parser

Parser.y defines the actual syntax of the language (i.e. how the tokens should be combined together). It starts with a %token definition which maps the token constructs to a shorter name to be used in the syntax definitions.

After this, the individual expressions are defined, usually recursively (see the definition for Exps and follow the individual sub-definitions).

To autogenerate the actual Parser.hs file from Parser.y, use the run_happy.sh script provided.

Verbose mode

Verbose debug info (parse tree) can be printed with the -v option. E.g. stack exec singlang-exe -- test-basic.lah -v.

Integration tests

Integration tests can be run with the run_integration_tests.sh script.