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70379d4e85
This PR adds a hook in the compiler and the engine to allow easy prototyping of new features.
In particular by using this hook, one can add a new feature in 1.dev with modifying:
compiler
type checkers (both Haskell and Scala)
archive Protobuf
archive decoder
In addition of development speed, this also adds a bit of confidence, as the peaces enumerated above are not touched when adding the feature: The feature can be added by modifying only 1.dev Daml standard library and Speedy.
aa7991f8 shows a use case of this hook.
CHANGELOG_BEGIN
CHANGELOG_END
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.. Copyright (c) 2021 Digital Asset (Switzerland) GmbH and/or its affiliates. All rights reserved.
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.. SPDX-License-Identifier: Apache-2.0
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Daml-LF experimental Builtin
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============================
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**This document is intended for Daml language maintainers.**
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The Daml compiler and the Daml Engine provides special hooks to easily
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add experimental Builtin functions to Daml-LF 1.dev. In particular,
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one can add such builtins by modifying only the Daml standard library
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and Speedy, but do not have to touch other parts of the stack such as
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archive Protobuf definitions, compilers, type checkers, and archive
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(de/en)coders.
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In addition of development speed, those hooks also adds some
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confidence non-development feature are not impacted when prototyping
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new Daml feature as few part of the stack had to be modified.
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Daml-LF Experimental Specification
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----------------------------------
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From Daml-LF perspective, experimental builtins are additional Daml-LF
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expressions of the form::
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ExperimentalBuiltin :
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`$` t τ
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Those expressions are typed as follows:
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————————————————————————————————————————————— TyExperimentalBuiltin
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Γ ⊢ `$` t τ : τ
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Daml Standard library Hook
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--------------------------
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From the Compiler side, the experimental builtins are added by
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convention in modules prefixed by `DA.Experimental` using primitive
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type prefixed by '$'. For instance consider the following module::
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module DA.Experimental.Example where
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answer: τ
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answer = primitive @"$ANSWER"
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The definition `answer` is translated in the Daml-LF definition:
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val DA.Experimental.Example:answer: τ = `$` "ANSWER" τ
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Speedy Hook
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-----------
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From the Speedy side, the Experimental Builtins are handle by HashMap
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::
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com.daml.lf.speedy.SBuiltin.SBExperimental.mapping : Map[String, SEBuilin]
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that associate to translate the expression ``(`$` t τ : τ)`` to
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``mapping(t)`` during Speedy compilation phase. By convention values
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of `mapping` should be completely written down inside the object
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`com.daml.lf.speedy.SBuiltin.SBExperimental`.
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Archive decoded
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---------------
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Experimental builtins are a development features. They are available
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in `1.dev` only. The deserialization process will reject Any Daml-LF
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stable or preview archive that contains Experimental builtins.
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.. Local Variables:
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.. eval: (flyspell-mode 1)
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.. eval: (set-input-method "TeX")
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.. End:
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