PREFIX

PREFIX is an esolang based entirely on prefix notation and function calling.

Language Constructions
In order to call a function and its arguments, one would do so like this: function arguments No parentheses are needed.

PREFIX has 3 basic language constructions:
 * 1) if condition, what to do: If condition is true, do what to do. What to do must be treated as one instruction.
 * 2) while execute condition, what to do: While executing execute condition returns true, do what to do.  Both execute condition and what to do must be treated as one instruction.
 * 3) seq...end: Executes everything between seq and end.  This is treated as one instruction.

Turing-completeness
In order to show that PREFIX is turing-complete, I have written a BF interpreter for it. The looping semantics may be off, though, so feel free to edit it.

define main: decl prog decl ip darray mem decl mp darray stack decl sp decl c set ip 0 set mp 0 while neq con prog readin "!" nop while lt ip len prog seq set c sstr prog ip #Set c to current character if eq c "+" set sarr mem mp add sarr mem mp 1 if eq c "-" set sarr mem mp sub sarr mem mp 1 if eq c ">" set mp add mp 1 if eq c "<" set mp sub mp 1 if eq c "." print toascii sarr mem mp 	if eq c "," set sarr mem mp fromascii readin if eq c "[" seq if neq sarr mem mp 0 seq set sarr stack sp ip 			set sp add sp 1 end if eq sarr mem mp 0 while neq sstr prog ip "]" set ip add ip 1 end if eq c "]" seq if neq sarr mem mp 0 seq set ip sarr stack sp 			set sp sub sp 1 end set ip add ip 1 end

Final Comments

 * PREFIX is a rather easy-to-code in esolang. Maybe it even isn't.
 * To implement PREFIX you will need a lot of stacks. Beware.