Introduction to SLAT

The Breakdown (part I)

• Introduction to SLAT
• Concrete and Abstract Syntax
• How to Use the Tokenizer
• Writing the Parser
• Deliverables for Part I
• Files to Download
• The BNF for SLAT and Java

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Introduction to SLAT

SLAT (Simple Language for Abstract Types) uses LISP-like declarations of abstract syntax to define programs.  It looks a lot like BNF and has basically the same functionality as Scheme's define-datatype.

As an introduction to abstract type declarations, here are some examples of SLAT declarations for a tree and a list:

    tree  ::= leaf ( int )
            | node ( String tree tree )

    int-list ::= null ()
               | cons ( int int-list )

The first declares a tree as either a leaf with an integer field or as a node with a string field and two tree fields.  The second declares an int-list as either null (no fields) or as a cons with an integer and int-list field.

SLAT declarations (like define-datatype) can have any number of variants.  For example, the lambda calculus looks like this in SLAT:

    exp ::= var-exp ( String )
          | lambda-exp ( String exp )
          | app-exp ( exp exp )

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