The syntax is based on s-expressions and is somewhat similar to lisp. It differs from lisp in that it does not support macros, is interpreted, and has no form of memory management. The language is expression based and only executes a single expression at a time. Expressions can be combined into files and executed one after the other. In files, lines that start with # are not read.
Anything that does not start with a ( or a $ will be treated as a string and left alone. Otherwise, it will be evaluated or substituted. If you want to treat something like a string no matter what, wrap it in quotes. For example: :
`(+ 1 1)'returns the string (+ 1 1) instead of 2.
There are a handful of built in functions.
- (+)
The addition operator. Adds all parameters together.
- (-)
The subtraction operator. Subtracts all parameters from the first.
- (*)
The multiplication operator. Multiplies all parameters together.
- (-)
The division operator. divides the first parameter by the rest.
- >
The greater than operator. Returns "1" if parameter 1 is greater than parameter 2. returns "0" otherwise.
- <
The less than operator. Returns "1" if parameter 1 is less than parameter 2. returns "0" otherwise.
- =
The equality than operator. Returns "1" if parameter 1 is equal to parameter 2. returns "0" otherwise.
- ++
The concatenation operator. Combines all parameters together as strings.
- at
The index operator. Gets the character from the string in the first parameter based on the number in the second. (at hello 3) returns l.
- id
Returns the result of the last parameter.
- isDef
Returns "1" if the first parameter is defined and "0" if not.
prints out each parameter separated by a space.
- input
Prints the first parameter followed by a space. Then grabs the next word the user enters and returns it.
- load
Executes the contents of each parameter. for example, (load std.lsp) would load the standard library.
- define
Associates a given value (in the second argument) with a name (in the first).
The standard library is pretty much empty but growing:
- (if <1 or 0> <block if 1> <block if 0>)
Executes the correct block depending on the condition. Ignores the other block of code. The first parameter must be a value while the other two must be functions.
- (for <initial value> <condition> <body>)
Executes the given condition every iteration. If true, it executes the body as well. If false, it returns the last value that the body returned. You can expect the last value returned by the body or the initial value to be stored in $p4.
- (game)
Play a guess the number game. Try to guess a number between 1 and 100.