# SI413 Fall 2026 Unit 1 Labs

language_name: gogo

notes_from_prof: |
    Language designed by Min Chun and reviewed by Sean Avilucea.
    This is a fairly straightforward language, with stripped-down
    syntax and a creative way to handle delimiter escapes.
    When there are no variables, we can use things which look like
    variables, to act as special commands!


example_program: |
    nono ask for a name and greet it.
    gogo "What is your name?"
    gogo "Hello ", ask

    nono read noun and adjective, reverse noun and print adjective
    gogo "Enter a noun and an adjective:"
    gogo <ask, " is not ", ask


    nono prints dcba, not badc
    gogo <("ab", "cd")

    nono prints he said "go"
    gogo "he said ""go"""


language_syntax: |
    There are four kinds of items:

    * A string: a double quote, any number of characters, and a closing
    double quote. Two double quotes in a row count as one double quote
    inside the string rather than closing it.

    * The word 'ask'

    * A single character '<' followed by an item

    * An expression surrounded by parentheses '()'

    An expression is one or more items separated by commas.

    A statement is the word 'gogo' followed by an expression

    A comment is the word 'nono' and everything after it up to the end of
    that line. A comment can appear on any line and is not part of a statement.

    A program is a sequence of one or more statements.


language_semantics: |
    Every item and expression evaluates to a string

    * A string evaluates to the characters between its quotes, counting each
    doubled double quote as one double quote.

    * Evaluating 'ask' reads a single line from the user. If there is no more input,
    the program stops with an error.

    * '<' followed by an item evaluates to that item's value with its characters
    in the reverse order. Since '<' only applies to one item, parentheses are
    needed to reverse a whole expression.

    * Items separated by commas evaluate to their values concatenated end to end.
    The items are evaluated left to right, so any 'ask' in them read their lines
    in that same order.

    A statement evaluates its expression, then prints the resulting characters.

    A program executes each statement in order from left to right.