The OCaml system release 4.00 Documentation and user's manual Xavier Leroy, Damien Doligez, Alain Frisch, Jacques Garrigue, Didier R´emy and J´er^omeVouillon July 26, 2012 Copyright © 2012 Institut National de Recherche en Informatique et en Automatique 2 Contents I An introduction to OCaml 9 1 The core language 11 1.1 Basics . 11 1.2 Data types . 12 1.3 Functions as values . 13 1.4 Records and variants . 14 1.5 Imperative features . 16 1.6 Exceptions . 18 1.7 Symbolic processing of expressions . 19 1.8 Pretty-printing and parsing . 20 1.9 Standalone OCaml programs . 23 2 The module system 25 2.1 Structures . 25 2.2 Signatures . 26 2.3 Functors . 27 2.4 Functors and type abstraction . 29 2.5 Modules and separate compilation . 31 3 Objects in OCaml 33 3.1 Classes and objects . 33 3.2 Immediate objects . 36 3.3 Reference to self . 37 3.4 Initializers . 38 3.5 Virtual methods . 38 3.6 Private methods . 40 3.7 Class interfaces . 42 3.8 Inheritance . 43 3.9 Multiple inheritance . 44 3.10 Parameterized classes . 44 3.11 Polymorphic methods . 47 3.12 Using coercions . 50 3.13 Functional objects . 54 3.14 Cloning objects . 55 3.15 Recursive classes . 58 1 2 3.16 Binary methods . 58 3.17 Friends . 60 4 Labels and variants 63 4.1 Labels . 63 4.2 Polymorphic variants . 69 5 Advanced examples with classes and modules 73 5.1 Extended example: bank accounts . 73 5.2 Simple modules as classes . 79 5.3 The subject/observer pattern . 85 II The OCaml language 89 6 The OCaml language 91 6.1 Lexical conventions . 91 6.2 Values . 95 6.3 Names . 97 6.4 Type expressions . 99 6.5 Constants . 103 6.6 Patterns . 103 6.7 Expressions . 106 6.8 Type and exception definitions . 117 6.9 Classes . 120 6.10 Module types (module specifications) . 126 6.11 Module expressions (module implementations) . 130 6.12 Compilation units . 133 7 Language extensions 135 7.1 Integer literals for types int32, int64 and nativeint . 135 7.2 Streams and stream parsers . 135 7.3 Recursive definitions of values . 135 7.4 Range patterns . 137 7.5 Assertion checking . 137 7.6 Lazy evaluation . 137 7.7 Local modules . 138 7.8 Recursive modules . 138 7.9 Private types . 139 7.10 Local opens . 142 7.11 Record notations . 142 7.12 Explicit polymorphic type annotations . 143 7.13 Locally abstract types . 143 7.14 First-class modules . 145 7.15 Recovering the type of a module . 146 7.16 Substituting inside a signature . 147 3 7.17 Explicit overriding in class definitions . 148 7.18 Generalized algebraic datatypes . 149 III The OCaml tools 153 8 Batch compilation (ocamlc) 155 8.1 Overview of the compiler . 155 8.2 Options . 156 8.3 Modules and the file system . 164 8.4 Common errors . 164 9 The toplevel system (ocaml) 169 9.1 Options . 170 9.2 Toplevel directives . 172 9.3 The toplevel and the module system . 174 9.4 Common errors . 174 9.5 Building custom toplevel systems: ocamlmktop . 175 9.6 Options . 175 10 The runtime system (ocamlrun) 177 10.1 Overview . 177 10.2 Options . 178 10.3 Dynamic loading of shared libraries . 180 10.4 Common errors . 180 11 Native-code compilation (ocamlopt) 183 11.1 Overview of the compiler . 183 11.2 Options . 184 11.3 Common errors . 192 11.4 Running executables produced by ocamlopt . 192 11.5 Compatibility with the bytecode compiler . 193 12 Lexer and parser generators (ocamllex, ocamlyacc) 195 12.1 Overview of ocamllex ..................................195 12.2 Syntax of lexer definitions . 196 12.3 Overview of ocamlyacc ..................................200 12.4 Syntax of grammar definitions . ..