Subscript

A small scripting language

Currently in javascript, other implementations tbd

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The gist:

I wanted to run user code but eval() is unsafe. Hence, a small language where user-provided code is relatively safe. (Even if the syntax is clunky as hell)

This language is, in it's current state, absolutely not portable. It is a thin wrapper over the behaviours of javascript and any further implementations will need to address that if they wish to be cross-compatible. But as a bare-bones scripting language for single-platform applications it is, maybe tolerable.

Usage:

Each statement consists of an instruction separated from the arguments by a colon, then the arguments separated by commas. Statements are separated by semicolons.

There are 6 instructions:

• set: a, b; - assigns the variable a the value of b. a must be an identifier, while b can be any value.
• call: a, ...; - calls the function stored in variable a with the arguments provided after.
• if: a[, b]; - if a is truthy, evaluate b (if available). If b is not provided, execution will continue until an end instruction is found.
• end; - ends the current conditional block.
• while: a[, b]; - while a is truthy, evaluate b (if available). If b is not provided, execution will continue until an end instruction is found.
• return a; - returns the provided value, ending execution.

There are 4 types of literal values:

• Strings ( "Hello" ) - A literal string value
• Numbers ( 0.2 ) - A literal number value
• Identifiers ( test ) - Refers to a variable in the scope
• true, false, null, and nil are special cases of variables that evaluate to what you'd expect.
• (note: true evaluates to the value true, true.something attempts to read the variable named true)
• Eval Strings ( call: print, "Hello!" ) - Evaluate the contents as their own script

There are several operators:

• a ^ b - power
• a % b - modulus
• a * b - multiply
• a / b - divide
• a + b - plus
• a - b - minus
• a > b - greater than
• a >= b - greater or equal to
• a < b - less than
• a <= b - less or equal to
• a & b or a && b - and
• a | b or a || b - or
• a = b or a == b - equal
• a != b - not equal

And a couple of unary operators that I hope work because I just sorta hacked them into the shunting yard algorithm:

• -a - arithmetical negation
• !a - logical negation