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| -rw-r--r-- | doc/lang.txt | 247 |
1 files changed, 183 insertions, 64 deletions
diff --git a/doc/lang.txt b/doc/lang.txt index a70067e..9375dd5 100644 --- a/doc/lang.txt +++ b/doc/lang.txt @@ -1,29 +1,38 @@ The Myrddin Programming Language Jul 2012 - Updated Dec 2015 + Updated Dec 2016 Ori Bernstein TABLE OF CONTENTS: 1. ABOUT - 2. NOTATION AND SEMANTICS - 2.1. Grammar + 2. LEXICAL CONVENTIONS + 2.1. EBNF-ish 2.2. As-If Rule - 3. LEXICAL CONVENTIONS - 3.1. Summary - 4. SYNTAX - 4.1. Declarations - 4.2. Literal Values - 4.3. Blocks - 4.4. Control Constructs - 4.5. Expressions - 4.6. Packages and Uses - 5. TYPES - 5.1. Data Types - 5.2. Type Inference - 5.3. Traits - 5.4. Generics - 6. GRAMMAR + 3. STRUCTURE: + 3.1. Whitespace and Keywords + 3.2. File Structure + 3.3. Declarations + 3.4. Packages and Uses + 3.5. Scoping + 4. TYPES + 4.1. Type Definitions + 4.2. Traits and Impls + 4.3. Generics + 4.4. Type Inference + 5. VALUES AND EXPRESSIONS + 5.1. Declarations + 5.2. Literal Values + 5.3. Control Constructs + 5.4. Expressions + 5.6. Packages and Uses + 6. CONTROL FLOW + 6.1. Blocks + 6.2. Conditionals + 6.3. Matches + 6.4. Looping + 6.5. Goto + 7. GRAMMAR 1. ABOUT: @@ -43,9 +52,9 @@ TABLE OF CONTENTS: ML, with ideas from too many other places to name. -2. NOTATION AND SEMANTICS: +2. LEXICAL CONVENTIONS: - 2.1. Grammar: + 2.1. EBNF-ish: Syntax is defined using an informal variant of EBNF. @@ -81,9 +90,9 @@ TABLE OF CONTENTS: as long as the result is observed as if the semantics specified were followed strictly. -3. LEXICAL CONVENTIONS: +3. STRUCTURE: - 3.1. Summary: + 3.1. Whitespace and Keywords: The language is composed of several classes of tokens. There are comments, identifiers, keywords, punctuation, and whitespace. @@ -123,9 +132,48 @@ TABLE OF CONTENTS: interchangable. They both are used to mark the end of logical lines, and will be uniformly referred to as line terminators. -4. SYNTAX OVERVIEW: + 3.2. File Structure: - 4.1. Declarations: + file: (decl | package | use | implstmt | traitdef | tydef)* + + A file is composed of a sequence of top level elements. These + top level elements consist of: + + - Declarations: + + These define a constant or a variable. It's worth noting + that Myrddin has no special syntax for declaring functions, + but instead assigns a closure to a variable or constant. + + - Package Definitions: + + These define the list of exported values from a file. As + part of compilation, all the exported names from a package + will get merged together from all the files being built + into that package. + + - Use Statements: + + These import symbols for use within the file. These symbols + come from either installed packages or files within the + project being compiled. + + - Type Definitions: + + These define new types. + + - Trait Definitions: + + These define traits, which are attributes on types that + may be implemented by impl functions. They define required + functions on the type. + + - Impl Statements: + + These define implementations of traits, allowing an + existing trait to be attached to an existing type. + + 3.3. Declarations: decl: attrs ("var" | "const" | "generic") decllist attrs: ("exern" | "pkglocal" | "$noret")+ @@ -204,6 +252,105 @@ TABLE OF CONTENTS: } + 3.4. Packages and Uses + + bareuse: use ident + quoteuse: use "<quoted string>" + pkgdef: "pkg" ident = decl* ";;" + + + There are two keywords for module system. 'use' is the simpler + of the two, and has two cases: + + use syspkg + use "localfile" + + The first form, which does not have the package name quoted, will + search the system include paths for the package listed. It does not + search relative to the file or the compiler working directory. + + The quoted form searches the current directory for a use file named + "localpkg" and imports it. + + The 'pkg' keyword allows you to define a (partial) package by + listing the symbols and types for export. For example, + + pkg mypkg = + type mytype + + const Myconst : int = 42 + const myfunc : (v : int -> bool) + ;; + + declares a package "mypkg", which defines three exports, "mytype", + "Myconst", and "myfunc". The definitions of the values may be + defined in the 'pkg' specification, but it is preferred to implement + them in the body of the code for readability. Scanning the export + list is desirable from a readability perspective. + + 3.5. Scoping: + + Myrddin is a lexically scoped language, with namespaces and types + defined in a way that facilitates separate compilation with minimal + burden on the linker. + + In Myrddin, declarations may appear in any order, and be used at any + point at which it is in scope. Any global symbols are initialized + before the program begins. Any nonglobal symbols are initialized + on the line where they are defined. This decision allows for slightly + strange code, but allows for mutually recursive functions with no + forward declarations or special cases. + + 3.5.1. Scope Rules: + + Myrddin follows the usual lexical scoping rules. A variable + may be defined on any line in the program. From there, any + expressions within that block and its sub blocks may refer + to it. + + The variables declared in constructs starting a block are + scoped to that block. For example, in `for var i = 0; ...`, + the variable `i` is scoped to the body of the for loop. + In the function `{x, y; funcbody()}`, the variables `x` and + `y` are scoped to the body of the function. + + Variables may shadow other variables, with the exception of + captured variables in pattern matches. The rules for matches + are covered in depth in section 6.3, but the rationale for + this is to prevent ambiguity when matching against defined + constants. + + 3.5.2. Capturing Variables: + + When a closure is created, it captures all of the variables + that it refers to in its scope by value. This allows for + simple heapification of the closure. + + For example: + + var x = 1 + var closure = {; -> x} + x++ + std.put("x: {}, closure(): {}\n", x, closure()) + + should output: + + x: 2, closure(): 1 + + 3.5.2. Namespaces: + + A namespace introduced by importing a package is gramatically + equivalent to a struct member lookup. The namespace is not + optional. + + 3.6. Program Initialization: + + Any file may define a single function name `__init__`. This function + will be invoked before `main` runs, and after the `__init__ `function + for all files included through use statements. + + +4. VALUES AND EXPRESSIONS: 4.3. Literal Values @@ -540,7 +687,13 @@ TABLE OF CONTENTS: postfixexpr: <prefixop> postfixexpr prefixexpr: atomicexpr <unaryop> - Myrddin expressions should be fairly familiiar to most programmers. + Myrddin expressions should be fairly familiar to most programmers. + Expressions are represented by a precedence sorted heirarchy of + binary operators. These operators operate on prefix expressions, + which in turn operate on postfix expressions. And postfix + expressions operate on parenthesized expressions, literals, or + values. + The operators are listed below in order of precedence, and a short summary of what they do is listed given. For the sake of clarity, 'x' will stand in for any expression composed entirely of subexpressions @@ -653,6 +806,9 @@ TABLE OF CONTENTS: match, again, given that it is never read from in the body of the match. + An represents a location in the machine that can be stored + to persistently and manipulated by the programmer. An obvious + example of this would be a variable name, although 4.6.3. Cast Expressions: @@ -747,6 +903,8 @@ TABLE OF CONTENTS: 4.6.4. Assignment: + The assignment operators + 4.6.5. Bitwise Expressions: 4.6.6: Arithmetic Expressons: @@ -756,45 +914,6 @@ TABLE OF CONTENTS: 4.6.8: Prefix Expressions - 4.8. Packages and Uses: - - bareuse: use ident - quoteuse: use "<quoted string>" - pkgdef: "pkg" ident = decl* ";;" - - - There are two keywords for module system. 'use' is the simpler - of the two, and has two cases: - - use syspkg - use "localfile" - - The first form, which does not have the package name quoted, will - search the system include paths for the package listed. It does not - search relative to the file or the compiler working directory. - - The quoted form searches the current directory for a use file named - "localpkg" and imports it. - - The 'pkg' keyword allows you to define a (partial) package by - listing the symbols and types for export. For example, - - pkg mypkg = - type mytype - - const Myconst : int = 42 - const myfunc : (v : int -> bool) - ;; - - declares a package "mypkg", which defines three exports, "mytype", - "Myconst", and "myfunc". The definitions of the values may be - defined in the 'pkg' specification, but it is preferred to implement - them in the body of the code for readability. Scanning the export - list is desirable from a readability perspective. - - 4.9. Scoping and Namespaces: - - 5. TYPES: 5.1. Data Types: |