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More specific reports about what is wrong when we know the correct next tokens to expect.
440 lines
14 KiB
Rust
440 lines
14 KiB
Rust
// Copyright 2017 Jeremy Wall <jeremy@marzhillstudios.com>
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//! Bottom up parser for precedence parsing of expressions separated by binary
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//! operators.
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use abortable_parser::combinators::eoi;
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use abortable_parser::{Error, Peekable, Result, SliceIter};
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use super::{non_op_expression, ParseResult};
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use crate::ast::*;
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macro_rules! abort_on_end {
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($i:expr) => {{
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if eoi($i.clone()).is_complete() {
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return Result::Fail(Error::new(
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format!("Expected Expression found End Of Input"),
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Box::new($i.clone()),
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));
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}
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}};
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}
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/// Defines the intermediate stages of our bottom up parser for precedence parsing.
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#[derive(Debug, PartialEq, Clone)]
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pub enum Element {
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Expr(Expression),
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Op(BinaryExprType),
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}
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make_fn!(
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dot_op_type<SliceIter<Token>, Element>,
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do_each!(
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_ => punct!("."),
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(Element::Op(BinaryExprType::DOT)))
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);
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make_fn!(
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math_op_type<SliceIter<Token>, Element>,
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either!(
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do_each!(
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_ => punct!("+"),
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(Element::Op(BinaryExprType::Add))),
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do_each!(
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_ => punct!("-"),
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(Element::Op(BinaryExprType::Sub))),
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do_each!(
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_ => punct!("*"),
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(Element::Op(BinaryExprType::Mul))),
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do_each!(
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_ => punct!("/"),
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(Element::Op(BinaryExprType::Div)))
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)
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);
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make_fn!(
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bool_op_type<SliceIter<Token>, Element>,
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either!(
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do_each!(
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_ => punct!("&&"),
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(Element::Op(BinaryExprType::AND))),
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do_each!(
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_ => punct!("||"),
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(Element::Op(BinaryExprType::OR)))
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)
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);
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fn parse_expression(i: SliceIter<Element>) -> Result<SliceIter<Element>, Expression> {
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let mut i_ = i.clone();
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abort_on_end!(i_);
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let el = i_.next();
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if let Some(&Element::Expr(ref expr)) = el {
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return Result::Complete(i_.clone(), expr.clone());
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}
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return Result::Fail(Error::new(
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format!(
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"Error while parsing Binary Expression Expected Expression got {:?}",
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el
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),
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Box::new(i_),
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));
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}
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fn parse_bool_operator(i: SliceIter<Element>) -> Result<SliceIter<Element>, BinaryExprType> {
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let mut i_ = i.clone();
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abort_on_end!(i_);
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let el = i_.next();
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if let Some(&Element::Op(ref op)) = el {
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match op {
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BinaryExprType::AND | BinaryExprType::OR => {
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return Result::Complete(i_.clone(), op.clone());
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}
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_other => {
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// noop
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}
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};
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}
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return Result::Fail(Error::new(
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format!(
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"Error while parsing Binary Expression Unexpected Operator {:?}",
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el
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),
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Box::new(i_),
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));
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}
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fn parse_dot_operator(i: SliceIter<Element>) -> Result<SliceIter<Element>, BinaryExprType> {
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let mut i_ = i.clone();
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abort_on_end!(i_);
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let el = i_.next();
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if let Some(&Element::Op(ref op)) = el {
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match op {
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&BinaryExprType::DOT => {
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return Result::Complete(i_.clone(), op.clone());
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}
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_other => {
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// noop
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}
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};
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}
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return Result::Fail(Error::new(
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format!(
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"Error while parsing Binary Expression Unexpected Operator {:?}",
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el
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),
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Box::new(i_),
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));
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}
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fn parse_sum_operator(i: SliceIter<Element>) -> Result<SliceIter<Element>, BinaryExprType> {
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let mut i_ = i.clone();
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abort_on_end!(i_);
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let el = i_.next();
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if let Some(&Element::Op(ref op)) = el {
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match op {
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&BinaryExprType::Add => {
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return Result::Complete(i_.clone(), op.clone());
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}
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&BinaryExprType::Sub => {
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return Result::Complete(i_.clone(), op.clone());
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}
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_other => {
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// noop
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}
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};
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}
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return Result::Fail(Error::new(
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format!(
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"Error while parsing Binary Expression Unexpected Operator {:?}",
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el
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),
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Box::new(i_),
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));
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}
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fn parse_product_operator(i: SliceIter<Element>) -> Result<SliceIter<Element>, BinaryExprType> {
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let mut i_ = i.clone();
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abort_on_end!(i_);
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let el = i_.next();
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if let Some(&Element::Op(ref op)) = el {
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match op {
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&BinaryExprType::Mul => {
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return Result::Complete(i_.clone(), op.clone());
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}
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&BinaryExprType::Div => {
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return Result::Complete(i_.clone(), op.clone());
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}
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_other => {
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// noop
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}
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};
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}
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return Result::Fail(Error::new(
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format!(
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"Error while parsing Binary Expression Unexpected Operator {:?}",
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el
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),
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Box::new(i_),
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));
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}
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make_fn!(
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compare_op_type<SliceIter<Token>, Element>,
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either!(
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do_each!(_ => punct!("=="), (Element::Op(BinaryExprType::Equal))),
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do_each!(_ => punct!("!="), (Element::Op(BinaryExprType::NotEqual))),
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do_each!(_ => punct!("~"), (Element::Op(BinaryExprType::REMatch))),
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do_each!(_ => punct!("!~"), (Element::Op(BinaryExprType::NotREMatch))),
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do_each!(_ => punct!("<="), (Element::Op(BinaryExprType::LTEqual))),
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do_each!(_ => punct!(">="), (Element::Op(BinaryExprType::GTEqual))),
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do_each!(_ => punct!("<"), (Element::Op(BinaryExprType::LT))),
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do_each!(_ => punct!(">"), (Element::Op(BinaryExprType::GT))),
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do_each!(_ => word!("in"), (Element::Op(BinaryExprType::IN))),
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do_each!(_ => word!("is"), (Element::Op(BinaryExprType::IS)))
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)
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);
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fn parse_compare_operator(i: SliceIter<Element>) -> Result<SliceIter<Element>, BinaryExprType> {
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let mut i_ = i.clone();
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abort_on_end!(i_);
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let el = i_.next();
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if let Some(&Element::Op(ref op)) = el {
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match op {
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&BinaryExprType::GT
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| &BinaryExprType::GTEqual
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| &BinaryExprType::LT
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| &BinaryExprType::LTEqual
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| &BinaryExprType::NotEqual
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| &BinaryExprType::REMatch
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| &BinaryExprType::NotREMatch
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| &BinaryExprType::Equal
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| &BinaryExprType::IS
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| &BinaryExprType::IN => {
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return Result::Complete(i_.clone(), op.clone());
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}
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_other => {
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// noop
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}
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};
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}
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return Result::Fail(Error::new(
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format!(
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"Error while parsing Binary Expression Unexpected Operator {:?}",
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el
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),
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Box::new(i),
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));
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}
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/// Parse a list of expressions separated by operators into a Vec<Element>.
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fn parse_operand_list<'a>(i: SliceIter<'a, Token>) -> ParseResult<'a, Vec<Element>> {
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// 1. First try to parse a non_op_expression,
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let mut _i = i.clone();
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let mut list = Vec::new();
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// 1. loop
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let mut firstrun = true;
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loop {
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// 2. Parse a non_op_expression.
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match non_op_expression(_i.clone()) {
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Result::Fail(e) => {
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// A failure to parse an expression
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// is always an error.
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if !firstrun {
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// if we have successfully parsed an element and an operator then
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// failing to parse a second expression is an abort since we know
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// for sure now that the next expression is supposed to be there.
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return Result::Abort(e);
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}
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return Result::Fail(e);
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}
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Result::Abort(e) => {
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// A failure to parse an expression
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// is always an error.
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return Result::Abort(e);
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}
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Result::Incomplete(i) => {
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return Result::Incomplete(i);
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}
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Result::Complete(rest, expr) => {
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list.push(Element::Expr(expr));
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_i = rest.clone();
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}
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}
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// 3. Parse an operator.
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match either!(
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_i.clone(),
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dot_op_type,
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math_op_type,
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compare_op_type,
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bool_op_type
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) {
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Result::Fail(e) => {
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if firstrun {
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// If we don't find an operator in our first
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// run then this is not an operand list.
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return Result::Fail(e);
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}
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// if we don't find one on subsequent runs then
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// that's the end of the operand list.
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break;
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}
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Result::Abort(e) => {
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// A failure to parse an operator
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// is always an error.
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return Result::Abort(e);
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}
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Result::Incomplete(i) => {
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return Result::Incomplete(i);
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}
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Result::Complete(rest, el) => {
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list.push(el);
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_i = rest.clone();
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}
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}
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firstrun = false;
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}
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return Result::Complete(_i, list);
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}
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make_fn!(
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parse_operator_element<SliceIter<Element>, BinaryExprType>,
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either!(
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parse_dot_operator,
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parse_sum_operator,
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parse_product_operator,
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parse_compare_operator,
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parse_bool_operator
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)
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);
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macro_rules! try_parse {
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($r:expr) => {
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match $r {
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Result::Abort(e) => return Result::Abort(e),
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Result::Fail(e) => return Result::Fail(e),
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Result::Incomplete(i) => return Result::Incomplete(i),
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Result::Complete(rest, op_type) => (rest, op_type),
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}
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};
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}
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fn parse_op(
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mut lhs: Expression,
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mut i: SliceIter<Element>,
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min_precedence: u32,
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) -> Result<SliceIter<Element>, Expression> {
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// Termination condition
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if eoi(i.clone()).is_complete() {
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return Result::Complete(i, lhs);
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}
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let (_, mut lookahead_op) = try_parse!(parse_operator_element(i.clone()));
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while !eoi(i.clone()).is_complete() && (lookahead_op.precedence_level() >= min_precedence) {
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// Stash a copy of our lookahead operator for future use.
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let op = lookahead_op.clone();
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// Advance to next element.
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i.next();
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let (rest, mut rhs) = try_parse!(parse_expression(i.clone()));
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i = rest;
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if !eoi(i.clone()).is_complete() {
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let (_, peek_op) = try_parse!(parse_operator_element(i.clone()));
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lookahead_op = peek_op;
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} else {
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}
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while !eoi(i.clone()).is_complete()
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&& (lookahead_op.precedence_level() > op.precedence_level())
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{
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let (rest, inner_rhs) =
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try_parse!(parse_op(rhs, i.clone(), lookahead_op.precedence_level()));
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i = rest;
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rhs = inner_rhs;
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// Before we check for another operator we should see
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// if we are at the end of the input.
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if eoi(i.clone()).is_complete() {
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break;
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}
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let (_, peek_op) = try_parse!(parse_operator_element(i.clone()));
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lookahead_op = peek_op;
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}
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let pos = lhs.pos().clone();
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lhs = Expression::Binary(BinaryOpDef {
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kind: op.clone(),
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left: Box::new(lhs.clone()),
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right: Box::new(rhs),
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pos: pos,
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});
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}
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return Result::Complete(i, lhs);
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}
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pub fn parse_precedence(i: SliceIter<Element>) -> Result<SliceIter<Element>, Expression> {
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match parse_expression(i) {
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Result::Abort(e) => Result::Abort(e),
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Result::Fail(e) => Result::Fail(e),
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Result::Incomplete(i) => Result::Incomplete(i),
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Result::Complete(rest, expr) => parse_op(expr, rest, 0),
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}
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}
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/// Parse a binary operator expression.
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pub fn op_expression<'a>(i: SliceIter<'a, Token>) -> Result<SliceIter<Token>, Expression> {
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// TODO(jwall): We need to implement the full on precedence climbing method here.
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let preparse = parse_operand_list(i.clone());
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match preparse {
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Result::Fail(e) => {
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let err = Error::caused_by(
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"Failed while parsing operator expression",
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Box::new(e),
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Box::new(i),
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);
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Result::Fail(err)
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}
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Result::Abort(e) => {
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let err = Error::caused_by(
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"Failed while parsing operator expression",
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Box::new(e),
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Box::new(i),
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);
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Result::Fail(err)
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}
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Result::Incomplete(i) => Result::Incomplete(i),
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Result::Complete(rest, oplist) => {
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let i_ = SliceIter::new(&oplist);
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let parse_result = parse_precedence(i_);
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match parse_result {
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Result::Fail(_e) => {
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let err = Error::new(
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"Failed while parsing operator expression",
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Box::new(rest.clone()),
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);
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Result::Fail(err)
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}
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Result::Abort(_e) => {
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let err = Error::new(
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"Abort while parsing operator expression",
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Box::new(rest.clone()),
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);
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Result::Abort(err)
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}
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Result::Incomplete(_) => Result::Incomplete(i.clone()),
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Result::Complete(_rest_ops, expr) => {
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if _rest_ops.peek_next().is_some() {
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panic!("premature abort parsing Operator expression!");
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}
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Result::Complete(rest.clone(), expr)
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}
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}
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}
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}
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}
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