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Note

Language maintanance has ended after 09/06/2022.

thank you for using this language.

Sesan Interpreter offical repository.

It can be used directly as a Web Playground, and can be built according to the build instructions.


Introduce

Start REPL

Download

git clone https://github.com/ky0422/sesan.git
cd sesan
# Install dependencies
npm i

# REPL
npm run start:repl

# You can also from a file.
npm run start:repl [file]

REPL commands

//command ...args

Command Description
exit Exit the repl
mode Change the mode (repl, lexer, parser, env)

Web Playground

README | Playground


Interpreter

Tokens

Token Identifier Token Identifier
EOF EOF ILLEGAL ILLEGAL
NUMBER NUMBER IDENT IDENT
TRUE TRUE STRING STRING
FUNCTION FUNCTION FALSE FALSE
ASSIGN = COMMENT COMMENT
MINUS - PLUS +
ASTERISK * BANG !
PERCENT % SLASH /
GT > LT <
NOT_EQUAL != EQUAL ==
COLON : COMMA ,
LPAREN ( SEMICOLON ;
LBRACE { RPAREN )
LBRACKET [ RBRACE }
LET LET RBRACKET ]
ELSE ELSE IF IF
WHILE WHILE RETURN RETURN
QUOTE " SINGLE_QUOTE '

Expressions

Except for If, Function Expression, all expressions must be preceded by a semicolon (;);

Expression Syntax Expression Syntax
Literal Block { [expr] }
If if (expr) [block] else [block]; Function func [name?](args) [block]
Call ident(args) Ident
Array [expr, expr, ...] Index ident[number]
Object { string: expr, ... } Assign [ident / index] = expr

Statements

Statement Syntax Statement Syntax
Let let ident = expr; While while (expr) [block];
Return return expr; Block { statement }

Priority

1 < ... < 10

Priority Number Operator
10 Nullish (??), Element (<-, .), Index ([])
9 Function Call
8 typeof, delete, throw, use, Prefix (!, -, +)
7 Multiplication (*, /, %)
6 Addition (+, -)
5 Comparison (>, <, >=, <=, in)
4 Equality (==, !=)
3 Logical (&&, ||)
2 Assignment (=)
1 ...

Operators

Operator Syntax Literal Type
+ ... + ... number, array, string, object
- ... - ... number
* ... * ... number
/ ... / ... number
% ... % ... number
== ... == ... number, string, boolean, array, object
!= ... != ... number, string, boolean, array, object
< ... < ... number
> ... > ... number
<= ... <= ... number
>= ... >= ... number
<- ... <- ... array, object, Any
. extends <- extends <-
?? ... ?? ... Any
in ... in ... string, number, object, string, number, object, array

Literal

Type Syntax
string "String", 'String'
number [-?]Number.[Number?]
boolean true, false
dict { [key (String, Number)]: [value (Any)], }
array [value (Any)]
func func [name?]([args]) [block]

Built-in functions

Function Arguments
import string
eval string
js string
to_s Any
to_n Any
to_b Any
to_a Any
options
regExp

Standard library

  • @std/
    • lib
    • io
      • print(args*) -> NULL
      • println(args*) -> NULL
    • array
      • push(array, value) -> array
      • pop(array) -> array
      • shift(array) -> array
      • unshift(array, value) -> array
      • slice(array, start, end) -> array
      • join(array, separator) -> string
      • forEach(array, callback) -> NULL
        • callback(value, index)
      • repeat(value, count) -> array, repeat(count) -> array
      • reduce(array, callback, initial) -> Any
        • callback(previous, current)
      • map(array, callback) -> array
        • callback(value, index)
    • util
      • funcTools -> object
      • length(array) -> number
      • match(value, [pattern], default) -> Any
      • ternary(condition, trueValue, falseValue) -> Any
    • [string]
      • split(string, separator) -> array
      • concat(args*) -> string
      • replace(string, pattern, replacement) -> string
      • subString(string, start, end) -> string
      • regExp(regexExpression, Options) -> string
        • regexExpression
          • pattern: [Regex Pattern]
          • flags: [Regex Flags]
        • Options
          • type: match, test, replace
          • str: string
          • replace?: string
      • regex(pattern, flags, string) -> function
        • match() -> string
        • test() -> boolean
        • replace(string, replace) -> string

Options

If sesan.config.json dose not exist in root (./), it extends Default.

Option Description Default
allowEval Allow eval() feature false
allowJavaScript Allow js() feature false
useStdLibAutomatically Use standard library automatically false
stderrPrefix Prefix for stderr true
stderrColor Color for stderr true
locale Locale en

Npm package

Warning

Some features may not be updated immediately.

when updating fatal errors, npm package is also updated immediately.

npm i @ky0422/sesan
import sesan, { NULL } from '@ky0422/sesan'

console.log(
    new sesan('let x = "World!"; println("Hello, " + x);', {
        useStdLibAutomatically: true,
    })
        .setBuiltins(new Map([['test', () => NULL]]))
        .applyBuiltins()
        .eval()
)

@std/ must exist in root (./).

curl -O https://raw.githubusercontent.com/ky0422/sesan/main/scripts/dl-stds.sh && . ./dl-stds.sh && rm ./dl-stds.sh

Examples



Documentation

For examples, see Examples


Variables

let <identifier> = <expression>;

<identifier> = <expression>;

extends <expression>

let foo = 1;

foo = 2;

variable names use camelCase or snake_case and, cannot use numbers as variable prefixes.


Data types

string

'Hello, World!'
"안녕, 세상아!"

Can start the string with ' or ", and the content supports all Unicode.

number

12345

3.141592

boolean

true, false

To convert another value to a boolean value, you can use the boolean, or use the !! prefix.

array

[1, 2, 3, 'Foo', 'Bar', [1, 2, 3]]

[1, 2, 3][1]    // 2

[1, 2, 3] <- 1  // 2

Array elements can be accessed via the index or element operator.

object

let object = {
    'foo': 'bar',
    bar: false,
    baz: [1, 2, 3],
    5: {
        x: func() {
            return 1;
        }
    }
}

object['foo']      // 'bar'
object.bar         // false
object <- 5 <- x() // 1

object <- qux      // UNDEFINED

Object is a pair of keys and values.

the key must be of type string or number, and the value can be any type.

object pairs are can be accessed via the index or element operator.

function

<arguments>: <identifier>, <identifier>, ...

func <identifier>(<arguments>) <block expression>;

func(<arguments>) <block expression>;

extends <block expression>

func foo(a, b) {
    return a + b;
}

let bar = func(a, b) {
    return a + b;
};

Functions can be declared with hard coding, and supports anonymous functions.

function names use camelCase or snake_case and, cannot use numbers as variable prefixes.

null

null

undefined

void <expression>

extends <expression>

Returns undefined after executing the expression.


Operators

<operator>: +, -, *, /, %, ==, !=, <, >, <=, >=, <-, ., ??, in

<left expression> <operator> <right expression>

extends <expression>

+ (Plus) Operator

The + operator is addition, and can add number, string, array, object.

number + number : Add the right operand to the left operand.

string + string : Concatenate the right operand to the left operand.

array + array : Concatenate the right operand to the left operand.

object + object : Add the right operand to the left operand. if there are duplicate keys, the right operand is overwritten.

- (Minus) Operator

The - operator is subtraction, and can subtract number.

* (Multiply) Operator

The * operator is multiplication, and can multiply number.

/ (Divide) Operator

The / operator is division, and can divide number.

% (Modulo) Operator

The % operator is modulo, and can modulo number.

==, !=, <, >, <=, >= Operators

The ==, !=, <, >, <=, >= operators are comparison operators, and can compare any type.

<-, . Operator

The element operator, which can access array or object elements.

[1, 2, 3] <- 1       // 2

[1, 2, 3].1          // 2

let object = {
    foo: {
        bar: 'baz'
    },
};

object <- foo <- bar   // 'baz'
object.foo.bar         // 'baz'

object['foo']['bar'] = 'qux';

Cannot reassign values ​​with the element operator, must use index.


Control flow

If

if <condition expression [boolean]> <block expression>
else <block expression>

if <condition expression [boolean]> <expression> else <expression>

extends <block expression>

if (condition) {
    implement();
} else if (condition) {
    implement();
} else implement();

Can use if, else and else if.

the condition of if is a boolean value, non-boolean values ​​should use !!.

!!2    // true
!!0    // false
!!null // false

While

while <condition expression [boolean]> <block expression>

extends <block expression>

while (condition) {
    implement();
}

If condition is true, the block expression is executed.

the condition of while is a boolean value, non-boolean values ​​should use !!.

does not support break and continue. This can be used with forEach.


Import

<use> <string>;

extends string

use './module/myLib';

Executes external source code and can import executed environments.

path follows the project root (default ./).

if .sesan is not included in path, .sesan will be added automatically.


Decorator

@<object>
<function> // func <identifier>(<arguments>) <block expression>;

extends <object>, <function>

let myObject = { foo: 'bar' };

@myObject
func myFunc() {
    println(this <- decorator <- foo);
}

myFunc();

decorator starts with the prefix @ and requires a object value.

after that, a function is required, anonymous functions cannot be used.


Built-in functions

import

import("./module/myLib");

extends import

eval

eval("5 + 5"); // 10

Execute the provided code. The code can access the current environment variable.

allowEval must be true.

this feature is a dangerous feature. be careful.

js

js("console.log('foo')");

allowJavaScript must be true.

this feature is a dangerous feature. be careful.

options

options(); // object

Get project options. this cannot be modified.


Standard library


IO

print

println("Hello, World!", 10);

Prints the provided value.

println

println("Hello, World!");

Prints the provided value with a new line (\n).

Utility

length

length([1, 2, 3]); // 3

length("Hello, World!"); // 13

Gets the length of an array or string.

match

println(match(3, [
    [ 1, func(v) { return value + 1; } ],
    [ 2, func(v) { return value + 2; } ]
], func(v) {
    println('nothing');
    return v * 10;
}));

to_s, to_n, to_b, to_a

to_s(1); // '1'
to_n('1'); // 1
to_b(1); // true
to_a({ foo: 'bar', bar: 1 }); // ['bar', 1]

ternary

ternary(true, "foo", "bar"); // "foo"
ternary(false, "foo", "bar"); // "bar"

If the supplied value is true, the left parameter is returned, otherwise the right parameter is returned.


Array

let arr = [1, 2, 3];

Arrays can contain values ​​of any type.

extends array

push

push(array, 4); // [1, 2, 3, 4]

Adds the provided values ​​to an array.

Since this is a deep copy, array is not changed.

pop

pop(array); // [1, 2]

Removes the last element of an array.

Since this is a deep copy, array is not changed.

shift

shift(array); // [2, 3]

Removes the first element of an array.

Since this is a deep copy, array is not changed.

unshift

unshift(array, 0); // [0, 1, 2, 3]

Adds the provided values ​​to the beginning of an array.

Since this is a deep copy, array is not changed.

slice

slice(array, 1, 3); // [2, 3]

Divide array by the range of the two provided parameters.

Since this is a deep copy, array is not changed.

join

join(array, ", "); // "1, 2, 3"

Adds array to the provided string.

Since this is a deep copy, array is not changed.

forEach

forEach(array, func (value, index) {
    println(index, value);
});

Iterate through the array.

callback is given a value to traverse and an index value.

forEach(true, func (i) {
    if (i % 2 == 0) { return true };

    if (i >= 10) { return false };

    println(i);
});

forEach can be used as a while statement.

provide a true value instead of an array for the parameter, and the index value is provided in the callback.

repeat

repeat(5); // [NULL, NULL, NULL, NULL, NULL]

repeat("foo", 3); // ["foo", "foo", "foo"]

If there is one parameter provided, iterates the null value by the number of provided values,

if there are two parameters, it iterates the first parameter by the second parameter.

reduce

reduce([ 1, 2, 3 ], func (prev, curr) prev + curr, 0);

Iterates through each element of the provided array, accumulating the return value of the callback and returning it.

can specify the initial value of the accumulated values.

map

map([1, 2, 3], func (x, _) x * 10);

Iterates through each element of the provided array, returning a new array with the return value of the callback.


String

split

split("foo bar baz", " "); // ["foo", "bar", "baz"]

Splits the supplied string into the second parameter.

concat

concat("foo", "bar", "baz"); // "foobarbaz"

Combines the provided parameters.

replace

replace("foo bar baz", " ", ", "); // "foo, bar, baz"

Replaces the value of the second parameter in the provided string with the value of the third parameter.

subString

subString("foo bar baz", 4, 7); // "bar"

Divides a string by the number of parameters provided.

regex

let pattern = regex('[a-z]', 'g', 'asdf');

println(pattern <- match());
println(pattern <- test());
println(pattern <- replace('b'));

Expression

<expression>;

Block Expression

<keywords> {
    implement();
}

<keywords> implement();

extends <keywords>, <if>

IIFE (Immediately Invoked Function Expression) pattern

(func () {
    implement();
})();

Statement

<let>, <return>, <while>, <block expression>, <expression statement>

extends <let>, <return>, <while>, <block expression>, <expression statement>

Keywords

<let>, <func>, <true>, <false>, <if>, <else>, <return>, <while>, <in>, <typeof>, <null>, <throw>, <delete>, <use>, <void>, <expr>

Not used, but may be added later

<class>, <for>, <const>

extends <let>, <func>, <true>, <false>, <if>, <else>, <return>, <while>, <in>, <use>, <void>, <expr>

typeof

<typeof> <expr>

Returns the type of the given expression.


typeof 10; // number
typeof 'foo'; // string
typeof true; // boolean
typeof {}; // object
typeof []; // array
typeof null; // null
typeof func() {}; // function
typeof void 0; // undefined

null

null; // NULL

throw

<throw> <expr>

Throws an error in the provided expression.

expr keyword

expr <expression>

extends expression

Evaluates the expression, and if the result is an error,

{
    'message': 'error message',
    'filename': 'file name',
    'line': 0,       // line number
    'column': 0,     // column number
    'error': true    // true if error
}

an Object containing the error message is returned.


throw 'Error'; // Error

delete

<delete> <expr>

Deletes the provided key from environment variables.


let a = 10;

delete a;

a; // Identifier 'a' is not defined.

Return

<keywords> {
    implement();

    return null;
} // `NULL`

<if> null; // `NULL`

Returns a value.

extends <keywords>, <if>, <block expression>


Todo

Warning

This plan is subject to change at any time.

Language maintanance has ended after 09/06/2022.

Syntax

  • switch (match) expression
    • [switch|match] <expr> { ...<case>, <default|_>: body }
      • case
        • <expr>: body
  • const statement
    • const <identifier> = <expr>;
  • class statement
    • class <identifier> { ...<method> }
      • method
        • <identifier> ( ...<parameter> ) <body>
  • for statement
    • for (<identifier> [in|of] <expr>) <body>
      • of
        • <expr> of <expr>
  • Bitwise operators
    • <expr> & <expr>
    • <expr> | <expr>
    • <expr> ^ <expr>
    • <expr> << <expr>
    • <expr> >> <expr>
    • <expr> >>> <expr>
  • Power operator
    • <expr> ** <expr>

Features

  • Compiling to JavaScript
  • CLI, Repl refectoring

About

Tiny interpreter in TypeScript

ky0422.github.io/sesan

Topics

language programming-language interpreter lang programming-lang

Resources

Readme

License

MIT license
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