Overlooker

Overlooker is an esoteric programming language by user:raiseafloppafan7741 in 2026.

Overview

There is a stack of functions. Popping from the stack or trying to access the top while it is empty halts the program and results in an error.

The entire program is treated as wrapped inside another function.

Command	Description
`[code]`	Pushes a lambda to the stack.
`!`	Pops a function `f` and a function `x` and invokes `f` with the parameter `x`.
`?`	Pops two functions, checks if they are syntactically equal, and if they are then pops two more functions `f` and `x` and invokes `f(x)`.
`&`	Pops a function `f` and another function `x` and "injects" `x` into `f` (overrides `f`'s parameter with `x`) and pushes the modified function without invoking it. Even if the overridden function is called with a different parameter, this will not change unless the override is removed.
`*`	Pops a function, removes its override (see above), and pushes it.
`-`	Pops two functions `f` and `g` and pushes `fg`. This is function composition.
`$`	Pushes the current function.
`@`	Pushes the argument passed to this function.
`.`	Pops the top of the stack.
`:`	Duplicates the top of the stack.
`%`	Swaps the top of the stack with the function below it.
`^`	Swaps the top of the stack with the function below the function below it.

[]$!

[][[]$[[]@!]&!]!