MCFunctionTypes.mc4

/* (c) https://github.com/MontiCore/monticore */
package de.monticore.types;

/* This is a MontiCore stable grammar.
 * Adaptations -- if any -- are conservative. */

import de.monticore.types.*;

/**
 * This grammar introduces function types
 * such as int -> int, (String -> int) -> void, (boolean, int) -> int
 * 
 * Function types are useful when functions shall be passed around 
 * as arguments or stored in a data structure (for later use).
 * This is typically the case in higher-order functional programming 
 * languages, such as Haskell.
 * The syntax here is actually inspired by Haskell.
 *
 * The language developer may choose the subset of types
 * of interest and combine these with the appropriate expressions
 *
 * This modularity of types and associated expressions greatly eases
 * the reuse of type structures in languages similar to Java / Haskell
 *
 * This grammar is part of a hierarchy of types, which can be found
 * under
 *   https://github.com/MontiCore/monticore/blob/dev/monticore-grammar/
 *                 src/main/grammars/de/monticore/types/Types.md
 *
 */

component grammar MCFunctionTypes
          extends MCBasicTypes {

  /** MCFunctionParTypes describes the parameters in brackets, i.e.
   * (int,long), (int), etc. but also allows ellipses at the end 
   * (int,long,Person...) 
  */
  MCFunctionParTypes =
    "(" (
    (MCType || ",")+
    (isElliptic:"...")?
    )? ")"
  ;

  /** ASTMCFunctionTypesType represents function types.
   *
   *  Any number of arguments is possible. 
   *  A -> B -> C  parses as usual as  A -> (B -> C) 
   */
  MCFunctionType implements MCType <80> =
    <rightassoc>
    MCFunctionParTypes "->"
    MCReturnType
  ;

  /** ASTMCUnaryFunctionType represents function types
   * that have exactly one parameter without any parentheses.
   *
   * This non-terminal is separate from MCFunctionType
   * to avoid parsing issues due to mutual left recursion.
   */
  MCUnaryFunctionType implements MCType <60> =
    <rightassoc>
    MCType "->"
    MCReturnType
  ;

}