#lang scribble/manual

@title{BSL Grammar}

This is the full BSL grammar. For a gentler introduction to the language,
please see the programs in the @tt{examples} folder.

NOTE: braces are not part of the grammar -- they are used to indicate
groupings of tokens. Also, @tt{<nl>} refers to @tt{<newline>}. Similarly,
@tt{<s-e>} refers to @tt{<simple-expr>}, 
@tt{<e>} refers to @tt{<expr>}, 
@tt{<t-e>} refers to @tt{<test-expr>}, and @tt{<id-l>} refers to @tt{<id-list>}.

@verbatim|{

<program>                ::= <def-expr-test-bang-nl>*
<def-expr-test-bang-nl>  ::= <def-expr-test-bang>
                          |  <newline>
<def-expr-test-bang>     ::= <definition>
                          |  <expr>
                          |  <test-case>
                          |  <big-bang>


<definition>             ::= <def-style-definition>
                          |  <fun-style-definition>
                          |  struct: <id> (<id-list>?) <newline>
<def-style-definition>   ::= def <id>: <expr>
<fun-style-definition>   ::= fun <id>(<id-list>?): <test-expr> <nl>
                          |  fun <id>(<id-l>?):<nl> <local-defs>* <e>
<id-list>                ::= <id> {, <id>}*
<local-defs>             ::= <def-style-definition>
                          |  <fun-style-definition>


<expr>                   ::= <test-expr> <newline>
                          |  <compound-expr>
<test-expr>              ::= <simple-expr>
                          |  <boolean-comparison>
                          |  <test-expr> and <test-expr>
                          |  <test-expr> or <test-expr>
                          |  not <test-expr>
<boolean-comparison>     ::= <simple-expr> <boolean-comp-simple>+
<boolean-comp-simple>    ::= <boolean-comp-op> <simple-expr>
<boolean-comp-op>        ::= < | <= | = | != | >= | > | in 
                          |  not in
<simple-expr>            ::= <value-expr>
                          |  + <simple-expr>
                          |  - <simple-expr>
                          |  <simple-expr> + <simple-expr>
                          |  <simple-expr> - <simple-expr>
                          |  <simple-expr> * <simple-expr>
                          |  <simple-expr> / <simple-expr>
                          |  <simple-expr> % <simple-expr>
                          |  <simple-expr> ** <simple-expr>
                          |  <value-expr>[<index-expr>]
                          |  <template-expr>
<index-expr>             ::= <s-e>
                          |  <s-e>:<s-e>
                          |  <s-e>:<s-e>:<s-e>
<template-expr>          ::= ..
                          |  ...
                          |  ....
                          |  .....
                          |  ......
<value-expr>             ::= empty
                          |  True
                          |  False
                          |  <id>
                          |  <number>
                          |  <image>
                          |  <string>
                          |  <list-expr>
                          |  (<test-expr>)
                          |  <id> (<id-list>?)
<list-expr>              ::= [ ]
                          |  [<simple-expr>{, <simple-expr>}*]
<compound-expr>          ::= <conditional>
<conditional>            ::= <if-expr> <else-expr>
                          |  <if-expr> <elif-expr>+ <if-end-marker>
<if-end-marker>          ::= <else-expr>
                          |  :done
<if-expr>                ::= if <test-expr>: <newline>? <expr>
<elif-expr>              ::= elif <test-expr>: <newline>? <expr>
<else-expr>              ::= else: <newline>? <expr>


                               
<test-case>              ::= test: <t-e> is: <t-e> <nl>
                          |  test: <t-e> is: <t-e> within: <t-e> <nl>
                          |  test_error: <t-e> <nl>
                          |  test_error: <t-e> matches: <t-e> <nl>
                          |  test_range: <t-e> from: <t-e> to: <t-e>



<big-bang>               ::= big_bang(<bb-clause>*) <newline>
<bb-clause>              ::= <id> = <test-expr> {, <bb-clause>}*

}|

@include-section{grammar/literals.scrbl}

@include-section{grammar/indent.scrbl}