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335 lines
10 KiB
Rust
335 lines
10 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, Result, SliceIter};
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use super::{non_op_expression, NomResult};
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use ast::*;
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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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MathOp(BinaryExprType),
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CompareOp(CompareType),
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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::MathOp(BinaryExprType::Add))),
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do_each!(
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_ => punct!("-"),
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(Element::MathOp(BinaryExprType::Sub))),
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do_each!(
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_ => punct!("*"),
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(Element::MathOp(BinaryExprType::Mul))),
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do_each!(
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_ => punct!("/"),
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(Element::MathOp(BinaryExprType::Div)))
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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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if eoi(i_.clone()).is_complete() {
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return Result::Abort(Error::new("Expected Expression found End Of Input", &i_));
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}
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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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&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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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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&i_,
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));
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}
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let el = i_.next();
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if let Some(&Element::MathOp(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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&i_,
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));
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}
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fn tuple_to_binary_expression(
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kind: BinaryExprType,
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left: Expression,
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right: Expression,
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) -> Expression {
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let pos = left.pos().clone();
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Expression::Binary(BinaryOpDef {
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kind: kind,
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left: Box::new(left),
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right: Box::new(right),
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pos: pos,
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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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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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&i_,
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));
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}
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let el = i_.next();
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if let Some(&Element::MathOp(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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&i_,
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));
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}
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/// do_binary_expr implements precedence based parsing where the more tightly bound
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/// parsers are passed in as lowerrule parsers. We default to any non_op_expression
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/// as the most tightly bound expressions.
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macro_rules! do_binary_expr {
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($i:expr, $oprule:ident, $lowerrule:ident) => {
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do_binary_expr!($i, run!($oprule), $lowerrule)
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};
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($i:expr, $oprule:ident, $lowerrule:ident!( $($lowerargs:tt)* )) => {
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do_binary_expr!($i, run!($oprule), $lowerrule!($($lowerargs)*))
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};
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($i:expr, $oprule:ident) => {
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do_binary_expr!($i, run!($oprule))
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};
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($i:expr, $oprule:ident!( $($args:tt)* )) => {
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do_binary_expr!($i, $oprule!($($args)*), parse_expression)
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};
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($i:expr, $oprule:ident!( $($args:tt)* ), $lowerrule:ident) => {
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do_binary_expr!($i, $oprule!($($args)*), run!($lowerrule))
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};
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($i:expr, $oprule:ident!( $($args:tt)* ), $lowerrule:ident!( $($lowerargs:tt)* )) => {
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do_each!($i,
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left => $lowerrule!($($lowerargs)*),
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typ => $oprule!($($args)*),
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right => $lowerrule!($($lowerargs)*),
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(tuple_to_binary_expression(typ, left, right))
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)
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};
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}
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make_fn!(
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sum_expression<SliceIter<Element>, Expression>,
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do_binary_expr!(
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parse_sum_operator,
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either!(trace_nom!(product_expression), trace_nom!(parse_expression))
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)
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);
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make_fn!(
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product_expression<SliceIter<Element>, Expression>,
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do_binary_expr!(parse_product_operator, trace_nom!(parse_expression))
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);
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make_fn!(
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math_expression<SliceIter<Element>, Expression>,
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either!(trace_nom!(sum_expression), trace_nom!(product_expression))
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);
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// TODO(jwall): Change comparison operators to use the do_binary_expr! with precedence?
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fn tuple_to_compare_expression(
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kind: CompareType,
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left: Expression,
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right: Expression,
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) -> Expression {
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let pos = left.pos().clone();
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Expression::Compare(ComparisonDef {
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kind: kind,
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left: Box::new(left),
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right: Box::new(right),
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pos: pos,
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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::CompareOp(CompareType::Equal))),
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do_each!(_ => punct!("!="), (Element::CompareOp(CompareType::NotEqual))),
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do_each!(_ => punct!("<="), (Element::CompareOp(CompareType::LTEqual))),
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do_each!(_ => punct!(">="), (Element::CompareOp(CompareType::GTEqual))),
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do_each!(_ => punct!("<"), (Element::CompareOp(CompareType::LT))),
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do_each!(_ => punct!(">"), (Element::CompareOp(CompareType::GT)))
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)
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);
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fn parse_compare_operator(i: SliceIter<Element>) -> Result<SliceIter<Element>, CompareType> {
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let mut i_ = i.clone();
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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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&i_,
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));
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}
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let el = i_.next();
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if let Some(&Element::CompareOp(ref op)) = el {
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return Result::Complete(i_.clone(), op.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 Unexpected Operator {:?}",
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el
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),
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&i,
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));
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}
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make_fn!(
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compare_expression<SliceIter<Element>, Expression>,
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do_each!(
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left => either!(trace_nom!(math_expression), trace_nom!(parse_expression)),
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typ => parse_compare_operator,
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right => either!(trace_nom!(math_expression), trace_nom!(parse_expression)),
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(tuple_to_compare_expression(typ, left, right))
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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>) -> NomResult<'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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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!(_i.clone(), math_op_type, compare_op_type) {
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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 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, 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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/// Parse a binary operator expression.
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pub fn op_expression<'a>(i: SliceIter<'a, Token>) -> NomResult<'a, Expression> {
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let preparse = parse_operand_list(i.clone());
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match preparse {
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Result::Fail(e) => Result::Fail(e),
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Result::Abort(e) => Result::Abort(e),
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Result::Incomplete(i) => Result::Incomplete(i),
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Result::Complete(rest, oplist) => {
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let mut i_ = SliceIter::new(&oplist);
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let parse_result = either!(
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i_,
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trace_nom!(compare_expression),
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trace_nom!(math_expression)
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);
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match parse_result {
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Result::Fail(e) => Result::Fail(e),
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Result::Abort(e) => Result::Abort(e),
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Result::Incomplete(i) => Result::Incomplete(i),
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Result::Complete(_, expr) => 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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