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Brief Scala Syntax Cheat Sheet

Table of contents

Syntax representation

The syntax represented in Extended Backus-Naur Form (EBNF), where:

 - | denotes alternative
 - [...] an option (0 or 1)
 - {...} a repetition (0 or more)

Types

Type = SimpleType | FunctionType

FunctionType = SimpleType '=>' Type | '(' [Types] ')' '=>' Type

SimpleType = identifier

Types = Type {',' Type}

A type can be:

  • A numeric type: Int, Double (and Byte, Short, Char, Long, Float),
  • The Boolean type with the values true and false,
  • The String type,
  • A Function type, like Int => Int, (Int, Int) => Int

Expressions

Expr = InfixExpr | FunctionExpr | if '(' Expr ')' Expr else Expr

InfixExpr = PrefixExpr | InfixExpr Operator InfixExpr

Operator = identifier

PrefixExpr = ['+'|'-'|'!'|'~'] SimpleExpr

SimpleExpr = identifier | literal | SimpleExpr '.' ident | Block

FunctionExpr = Bindings '=>' Expr

Bindings = identifier[':' SimpleType] | '('[Binding {',' Binding}] ')'

Binding = ident [':' Type]

Block = '{' {Def ';'} Expr '}'

Expressions can be:

  • An identifier such as x, isGoodEnough
  • A literal, like 0, 1.0, "abc"
  • A function application, like sqrt(x)
  • An operator application , like -x, y+x
  • A selection, like math.abs
  • A conditional expr, like if(x<0) -x else x
  • A block, like {val x = math.abs(y); x*2}
  • An anonymous function, like x=>x+1

Definitions

Def = FunctDef | ValDef

FunctDef = def identifier{ '('[Parameters]')' }[: Type] '=' Expr

ValDef = val identifier[':' Type] '=' Expr

Parameters = Parameter{',' Parameter}

Parameter = identifier ':' ['=>'] Type

A definition can be:

  • A function definition, like def square(x: Int) = x*x
  • A value definition*, like val y = square(2)

A parameter can be:

  • A call-by-value parameter, like (x: Int)
  • A call-by-name parameter, like (y: => Double)

References

Coursera
Martin Odersky.
Functional Programming Principles in Scala
[Online] Available from: https://class.coursera.org/progfun-003
[Accessed: 06 August 2014].

Coursera
Martin Odersky.
Functional Programming Principles in Scala.
Lecture 2.4 - Scala Syntax Summary (4:13).
[Online] Available from:https://class.coursera.org/progfun-003/lecture/41
[Accessed: 06 August 2014].

Scala
[Online] Available from: http://www.scala-lang.org/
[Accessed: 06 August 2014].

Extended Backus–Naur Form
[Online] Available from: http://en.wikipedia.org/wiki/Extended_Backus%E2%80%93Naur_Form
[Accessed: 09 August 2014].

The Scala Language Specification Version 2.9
Martin Odersky.
[Online] Available from: http://www.scala-lang.org/docu/files/ScalaReference.pdf
[Accessed: 10 August 2014].