83 lines
2.5 KiB
Text
83 lines
2.5 KiB
Text
/-
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Copyright (c) 2018 Microsoft Corporation. All rights reserved.
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Released under Apache 2.0 license as described in the file LICENSE.
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Author: Sebastian Ullrich
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Term-level parsers
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-/
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prelude
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import init.lean.parser.token
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namespace lean
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namespace parser
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open combinators parser.has_view monad_parsec
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@[derive monad alternative monad_reader monad_state monad_parsec monad_except monad_rec monad_basic_read]
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def command_parser_m := rec_t unit syntax basic_parser_m
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abbreviation command_parser := command_parser_m syntax
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@[derive monad alternative monad_reader monad_state monad_parsec monad_except monad_rec monad_basic_read]
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def term_parser_m := rec_t nat syntax command_parser_m
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abbreviation term_parser := term_parser_m syntax
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/-- A term parser for a suffix or infix notation that accepts a preceding term. -/
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@[derive monad alternative monad_reader monad_state monad_parsec monad_except monad_rec monad_basic_read]
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def trailing_term_parser_m := reader_t syntax term_parser_m
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abbreviation trailing_term_parser := trailing_term_parser_m syntax
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/-- Access leading term -/
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def leading : trailing_term_parser := read
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instance : has_tokens leading := ⟨[]⟩
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instance : has_view leading syntax := default _
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@[derive parser.has_tokens parser.has_view]
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def hole.parser : term_parser :=
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node! hole [hole: symbol "_"]
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@[derive parser.has_tokens parser.has_view]
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def app.parser : trailing_term_parser :=
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node! app [fn: leading, arg: recurse max_prec]
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@[derive parser.has_tokens parser.has_view]
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def leading.parser :=
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any_of [
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hole.parser
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]
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@[derive parser.has_tokens parser.has_view]
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def trailing.parser : trailing_term_parser :=
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any_of [
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app.parser
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]
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/- Pratt parser -/
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def curr_lbp : term_parser_m nat :=
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do some tk ← monad_lift match_token | pure 0,
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pure tk.lbp
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def trailing_loop (rbp : nat) : nat → syntax → term_parser
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| 0 _ := error "unreachable"
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| (n+1) left := do
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lbp ← curr_lbp,
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if rbp < lbp then do
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left ← trailing.parser.run left,
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trailing_loop n left
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else
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pure left
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-- While term.parser does not actually read a command, it does share the same effect set
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-- with command parsers, introducing the term-level recursion effect only for nested parsers
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def term.parser : command_parser :=
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with_recurse 0 $ λ rbp, do
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left ← leading.parser,
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n ← remaining,
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trailing_loop rbp (n+1) left
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instance term.parser.tokens : has_tokens term.parser :=
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⟨has_tokens.tokens leading.parser ++ has_tokens.tokens trailing.parser⟩
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instance term.parser.view : has_view term.parser syntax :=
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default _
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end parser
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end lean
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