Functional Programming Principles in Scala in 2013/Sep Week 2
week 2の備忘録
# Higher Order Functions
- とりあえず、こいつがScalaのEBNF (Extended Backus-Naur form)だ
- | はalternative, [...]はoption, {...}はrepetitionを表す
- varがない。functionalな部分について、ということか？
// Types
Type = SimpleType
| FunctionType
FunctionType = SimpleType '=>' Type
| '(' [Types] ')' '=>' Type
SimpleType = Ident
Types = Type {',' Type}
// Expressions
Expr = InfixExpr
| FunctionExpr
| if '(' Expr ')' Expr else Expr
InfixExpr = PrefixExpr
| InfixExpr Operator InfixExpr
Operator = Ident
PrefixExpr = ['+' | '-' | '!' | '~'] SimpleExpr
SimpleExpr = ident
| literal
| SimpleExpr '.' ident
| Block
FunctionExpr = Bindings '=>' Expr
Bindings = ident [':' SimpleType]
| '(' [Binding {',' Binding }] ')'
Binding = ident [':' Type]
Block = '{' {Def ';'} Expr '}'
// Definitions
Def = FunDef | ValDef
FunDef = def ident {'(' [Parameters] ')'} [':' Type] '=' Expr
ValDef = val ident [':' Type] '=' Expr
Parameter = ident ':' [ '=>' ] Type
Parameters = Parameter {',' Parameter }
- (x: Int)はcall-by-value, (x: => Int)はcall-by-name
- classで型宣言できる
class Rational(x: Int, y: Int) {
def numer = x
def denom = y
}