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41 lines
1.8 KiB
Plaintext
41 lines
1.8 KiB
Plaintext
{0 Default calculus}
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This module contains a generic AST structure, various type definitions and
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helpers that are reused in various passes of the compiler.
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{1 The {!modules: Shared_ast.Definitions} module}
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The main module {!modules: Shared_ast.Definitions} is exposed at top-level of
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the library (so that [open Shared_ast] gives access to the structures). It
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defines literals, operators, and in particular the type {!types:
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Shared_ast.naked_gexpr}.
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The {!types: Shared_ast.naked_gexpr} type regroups all the cases for the {{:
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../dcalc.html} Dcalc} and {{: ../lcalc.html} Lcalc} ASTs, with unconstrained
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annotations (used for positions, types, etc.). A GADT is used to eliminate
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irrelevant cases, so that e.g. [(dcalc, _) naked_gexpr] doesn't have the [ERaise] and
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[ECatch] cases, while [(lcalc, _) naked_gexpr] doesn't have [EDefault].
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For example, Lcalc expressions are then defined as
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[type 'm naked_expr = (Shared_ast.lcalc, 'm mark) Shared_ast.naked_gexpr].
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This makes it possible to write a single function that works on the different
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ASTs, by having it take a [('a, _) naked_gexpr] as input, while retaining a much
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stricter policy than polymorphic variants.
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The module additionally defines the encompassing [scope] and [program]
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structures that are also shared between different compiler passes.
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{1 Helper library}
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The {!modules: Shared_ast.Var} defines ['e Var.Set.t] and [('e, _) Var.Map.t]
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types that are useful to handle variables for the different ['e] expression
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types without re-instanciating [Set.Make] and [Map.Make] each time.
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{!modules: Shared_ast.Expr} contains various helpers to build well-formed
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expressions, and for traversal.
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{!modules: Shared_ast.Scope Shared_ast.Program} are dedicated to handling the
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program structure around expressions. Note that these don't make sense for the
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early compiler passes (up to [Scopelang]).
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