Groovy for Domain-specific Languages - Second Edition

Introduction to DSLs and Groovy

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This produces the following output:

[fileUnder: Software Development, title: Groovy for DSL, author: Fergal
Dearle]

Groovy for DSL

Groovy for DSL

Closures

Closures are one of the most powerful language features in Groovy. Closures are
anonymous code fragments that can be assigned to a variable. Closures can be
invoked by the call method as follows:

def biggest = { number1, number2 ->

number1<number2?number2:number1

}

// We can invoke the call method of the Closure class

def result = biggest.call(7, 1)

println result

// We can use the closure reference as if it were a method

result = biggest(3, 5)

println result

// And with optional parenthesis

result = biggest 13, 1

println result

Closures can contain multiple statements and can therefore be as complex as you
like. In the following example, we iterate through a list looking for the biggest
number, and return it when we are done:

def listBiggest = { list ->

def biggest = list[0]

for( i in list)

if( i > biggest)

biggest = i

return biggest

}

def numberList = [ 8, 6, 7, 5, 3, 9]

println listBiggest( numberList)

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