DSLs in Action

377 Pages·2010·6.19 MB·English

by  Debasish Ghosh

IN ACTION
Debasish Ghosh
FOREWORD BY JONAS BONÉR
M A N N I N G
DSLs in Action

DSLs in ACTION
DEBASISH GHOSH
MANNING
Greenwich
(74° w. long.)
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ISBN 9781935182450
Printed in the United States of America
1 2 3 4 5 6 7 8 9 10 – MAL – 16 15 14 13 12 11 10
To my grandfather, who taught me my first alphabet
brief contents
PART 1 INTRODUCING DOMAIN-SPECIFIC LANGUAGES . ...............1
1 ■ Learning to speak the language of the domain 3
2 ■ The DSL in the wild 25
3 ■ DSL-driven application development 54
PART 2 IMPLEMENTING DSLS ..................................................85
4 ■ Internal DSL implementation patterns 87
5 ■ Internal DSL design in Ruby, Groovy, and Clojure 128
6 ■ Internal DSL design in Scala 166
7 ■ External DSL implementation artifacts 211
8 ■ Designing external DSLs using Scala parser
combinators 241
PART 3 FUTURE TRENDS IN DSL DEVELOPMENT.....................275
9 ■ DSL design: looking forward 277
vvii
contents
foreword xiii
preface xv
acknowledgments xvii
about the book xix
PART I INTRODUCING DOMAIN-SPECIFIC LANGUAGES .....1
1 Learning to speak the language of the domain 3
1.1 The problem domain and the solution domain 4
The problem domain 4 ■ The solution domain 4
1.2 Domain modeling: establishing a common vocabulary 6
Benefits of a common vocabulary 7
1.3 Introducing DSLs 8
What’s a DSL? 10 ■ Popular DSLs in use 12
Structure of a DSL 14
1.4 Execution model of a DSL 15
1.5 Classifying DSLs 17
Internal DSLs 18 ■ External DSLs 18
Nontextual DSLs 19
vii
viii CONTENTS
1.6 When do you need a DSL? 20
The advantages 20 ■ The disadvantages 21
1.7 DSLs and abstraction design 22
1.8 Summary 23
1.9 References 24
2 The DSL in the wild 25
2.1 Building your first Java DSL 26
Setting up the common vocabulary 27 ■ Your first
Java implementation 28
2.2 Making friendlier DSLs 32
Externalizing the domain with XML 32 ■ Groovy:
a more expressive implementation language 33
Executing the Groovy DSL 35
2.3 DSL implementation patterns 36
Internal DSL patterns: commonality and variability 37
External DSL patterns: commonality and variability 45
2.4 Choosing DSL implementations 50
2.5 Summary 52
2.6 References 53
3 DSL-driven application development 54
3.1 Exploring DSL integration 55
Why you should care about DSL integration 56
3.2 Internal DSL integration patterns 58
Using the Java 6 scripting engine 60 ■ Using a DSL
wrapper 64 ■ Language-specific integration
features 73 ■ Spring-based integration 75
3.3 External DSL integration patterns 76
3.4 Handling errors and exceptions 78
Naming an exception 79 ■ Handling incorrect typing errors 80
Handling exceptional business conditions 81
3.5 Managing performance 82
3.6 Summary 83
3.7 References 84
CONTENTS ix
PART II IMPLEMENTING DSLS ......................................85
4 Internal DSL implementation patterns 87
4.1 Filling your DSL toolbox 88
4.2 Embedded DSLs: patterns in metaprogramming 90
Implicit context and Smart APIs 91 ■ Reflective
metaprogramming with dynamic decorators 96
Reflective metaprogramming with builders 102
Lessons learned: metaprogramming patterns 105
4.3 Embedded DSLs: patterns with typed abstractions 106
Higher-order functions as generic abstractions 106
Using explicit type constraints to model domain logic 113
Lessons learned: thinking in types 117
4.4 Generative DSLs: boilerplates for runtime
generation 118
How generative DSLs work 118 ■ Ruby metaprogramming
for concise DSL design 119
4.5 Generative DSLs: macros for compile-time code
generation 122
Metaprogramming with Clojure 122 ■ Implementing the
domain model 123 ■ The beauty of Clojure macros 125
4.6 Summary 126
4.7 References 127
5 Internal DSL design in Ruby, Groovy, and Clojure 128
5.1 Making DSLs concise with dynamic typing 129
Readability 130 ■ Duck typing 131 ■ Metaprogramming—
again! 133 ■ Why Ruby, Groovy, and Clojure? 134
5.2 A trade-processing DSL in Ruby 135
Getting started with an API 136 ■ A little bit of
monkey-patching 139 ■ Rolling out a DSL interpreter 140
Adding domain rules as decorators 143
5.3 The order-processing DSL: the final frontier in
Groovy 148
The order-processing DSL so far 148 ■ Controlling the scope of
metaprogramming 149 ■ Rounding it off 152