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| This page gives an in-depth specification of the DomTool language. Most members would probably prefer the more informal presentation in DomTool/UserGuide. [[TableOfContents()]] = Source code = For a complete, precise, and accurate grammatical specification, see the lexer and parser specifications `src/domtool.lex` and `src/domtool.grm` in the DomTool source code. See `src/tycheck.sml` for the type-checker implementation. ["DomTool/Building"] has information on obtaining the source. = Token conventions = In the grammars that follow, we use these lexical token class names: || '''Name''' || '''Description''' || || `Int` || Integer constant || || `String` || String constant (enclosed in double quotes) || || `Symbol` || Identifier starting with a lowercase letter || || `CSymbol` || Identifier starting with a capital letter || = Predicates = DomTool uses '''predicates''' to describe in what contexts an action may occur. For instance, web-related actions should only occur inside the scope of a virtual host directive. Predicates are built up following the grammar in the table below, using the letter `P` as the non-terminal for predicates. Meanings are given as statements that must hold about the context where an action is found. The context is represented as a stack of '''context IDs''' which have been declared with `context` declarations. || '''Syntax''' || '''Description''' || '''Meaning''' || || `Root` || Root || The stack is empty. || || `CSymbol` || Context ID || `CSymbol` is on the top of the stack. || || `^P` || Suffixes || Some (not necessarily strict) suffix of the stack matches `P`. || || `!P` || Not || The stack ''doesn't'' match `P`. || || `P1 & P2` || And || The stack matches both `P1` and `P2`. || || `(P)` || Grouping || Identical to `P` || = Types = Types describe expressions. As is standard in statically-typed programming languages, they are used only for validation purposes and have no real effect on the "output" of a program. The following table gives the grammar of types `T`. The section on expressions will give the meanings of types in terms of which expressions have which types. || '''Syntax''' || '''Description''' || || `Symbol` || Extern type || || `[T]` || List of `T`s || || `T1 -> T2` || Function from `T1` to `T2` || || `[P]` || Action allowed only when `P` is satisified; requires no environment variables on input and writes none of its own || || `[P] {CSymbol1 : T1, ..., CSymbolN : TN}` || Action that requires environment variables `CSymbol1`, ..., `CSymbolN` to have the given types when run || || `[P] {CSymbol1_1 : T1_1, ..., CSymbol1_N : T1_N} => {CSymbol2_1 : T2_1, ..., CSymbol2_M : T2_M}` || Like the last case, but the second set of typed environment variables describes what the action will write || || `P => T` || A nested action that requires that its nested configuration satisfy `P`; `T` should be some action type || || `(T)` || Grouping || = Expressions = Here is the grammar of expressions `E`. As is standard in ML-family languages and Haskell, juxtaposition is used to represent function application, with application associating to the left. || '''Syntax''' || '''Description''' || '''Typing''' || || `Int` || Integer constant || `G |- Int : int` || || `String` || String constant || `G |- String : string` || || `[E1, ..., EN]` || List || If `G |- Ei : T` for each `Ei`, then `G |- [E1, ..., EN] : [T]`. || || `Symbol` || Variable || `G1, Symbol : T, G2 |- Symbol : T`. || || `E1 E2` || Application || If `G |- E1 : T1 -> T2` and `G |- E2 : T1`, then `G |- E1 E2 : T2`. || || `\ Symbol -> E` || Abstraction (inferred domain type) || If `G, Symbol : T1 |- E : T2`, then `G |- \ Symbol -> E : T1 -> T2`. || || `\ Symbol : (T1) -> E` || Abstraction (explicit domain type) || If `G, Symbol : T1 |- E : T2`, then `G |- \ Symbol : (T1) -> E : T1 -> T2`. || || `CSymbol = E` || Environment variable set || See subsection on actions || || `Symbol <- CSymbol; E` || Environment variable get || See subsection on actions || || `E1; E2` || Sequencing || See subsection on actions || || `E1 where E2 end` || Local bindings || See subsection on actions || || `let E1 in E2 end` || Local bindings || See subsection on actions || || `E1 with E2 end` || Nested action || See subsection on actions || || `E1 with end` || Empty nested action || See subsection on actions || || `E1 where E2 with E3 end` || Nested action with local bindings || See subsection on actions || || `E1 where E2 with end` || Empty nested action with local bindings || See subsection on actions || || `\\ Symbol : P -> E` || Nested action abstraction || See subsection on actions || |
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