Simple example recursive-descent parser for expressions.

• data
• exp.sml
• main.sml

exp.sml -- parser

The lexical analysis function converts a char list into a Symbol list; to see this try, e.g.,

    use "exp.sml";

    lexical(explode "(1+2)*3-4/5+x");

The parser takes a Symbol list and produces a parse tree : Exp, e.g.,

    expression(lexical(explode "(1+2)*3-4/5+x"));

main.sml -- parse text from a file

wrapper for the parser, asks for a file name, opens it, calls the parser, e.g.,

    use "main.sml";

    run "data";

 

Note, these expressions include arithmetic (+, -, *, /), relational (=, <>, <=, >=, < >), and logical (and, or, not) operators.

 

And there is a syntax (and semantics) for a small programming language [here].