Open Source Bridge

During this talk, we will survey real-world implementations of JIT-compiled embedded DSLs and their applications.

Speaker: Jeremy Voorhis

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Contributed notes

Domain-Specific Languages (DSLs) as jargon for shared use by domain experts, programmers. c.f. Landin's "The Next 700 Programming Languages," where he creates a "you know what I mean" meta-DSL.

In a DSL, your model should represent domain concepts. You should use the language of the experts.

Interpreted DSLs are easy to build / maintain. Good choice "in the absence of performance requirements," he says cheekily.  ;-)

Compiled DSLs have an initial overhead. But they can generate code in another target language, or even (through JIT) machine code.

External vs. embedded DSL: is your DSL a language or a library?

Examples: 3 musical DSLs

• Csound: list of musical events in a score
• ChucK: more programming-like
• Faust: wire up DSP steps in a graphical block diagram

Using LLVM

• Suite of compiler backend tools
• Generate intermediate representation (IR)
  • Uses single-assignment style, types, modules, metadata
  • Think of it as a target-independent, type-safe assembly language
• Transform IR and generate machine code
• Backends for many languages
  • Ruby example that builds up the IR in a Builder-like syntax
  • I put a DSL in your DSL, so you can ...

Introducing Siren

• JITtable music DSL
• Can process audio in realtime

Q. "How would you slur notes?" A. "Maybe I'll have an answer for that, but not today."

Modeling sound

• Sound as function from Time (Real) to Amplitude (Real)
• Programmer can create a new kind of sound by defining needed parameters + "render" function to return amplitude at a particular relative time
• A programming language = lambda calculus + handy constants
• Siren generates and walks an AST from Ruby code, generating IR through the builder-like syntax
  • c.f. Hutton's "Fold and Unfold for Denotational Semantics"
• Generates some IR, some C (for easy calls to portaudio)
  • Easy to pass generated code to the runtime
• Demo of Siren playing Satie's Gymnopaedie

For more, see http://github.com/jvoorhis