SASLCompiler

Language manual

JSASL is a dialect of the St. Andrews Static Language. It is a turing complete, functional language with 5 basic primitive types: numbers, strings, booleans, pairs and nil. The code is parsed, tokenized, checked for grammar errors and than translated into a graph, which is subsequently reduced and lazily evaluated.

Simple expressions

Simple expressions can be naturally stated. JSASL supports +, -, * and / (div, not floating point division)

Brackets

Expressions can be nested using ().

Strings

Strings are primitive types, stated in "" that can be concatened using +.

Booleans

Boolean operators are and, or and not. Numbers can be compared with =, ~=, <, >, <= and >=. Strings and booleans also support = and ~=.

If-then-else

If-then-else blocks have to evaluate to something, that means the else branch must be present.

Definitions

Definitions can be stated before a dot .. They consist of the keyword def, a name for the definition and the assignment operator =

Local variables

In addition to the global definitions using def, variables can be locally defined by using where. In a where block, definitions are separated by ;. Local where variables override global variables.

Functions

Functions can be defined like any other definition. Arguments are stated after the identifier, as seen above.

Recursion

The definition of recursive functions is straightforward.

(Loops)

Loops have to be defined as (end-)recursive functions.

Lists

Lists are linked lists, where every node (a pair) consist of a value and a pointer to its successor. Lists can be defined by square brackets.

Lists (continued)

A list is terminated by its last node pointing to nil as its successor. Instead of creating this structure implicitly by using the notation described above, lists can also be defined explicitly with the cons operator :.

Note how, in the code above, the last pair points to nil as its last element. The code above can be best understood by reading it as 1:(2:(3:(4:(5:(6:nil))))).

Lists (continued)

The head element (the first element of a pair) can be retrieved via the built-in hd function. The rest of the list (the second element of a pair) can be retrieved via the built-in tl function.

Infinite lists

Lists are evaluated lazily. This means that you can define lists by defining a pair where the second pair is a function constructing another pair. List elements can than be accessed without evaluating the whole list beforehand. More specifically, this means that you can define lists with infinite length, like the list of all natural numbers starting at n.