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doc: explain that matching is greedy without backtracking #744

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merged 1 commit into from Nov 29, 2022
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doc: explain that matching is greedy without backtracking #744

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13 changes: 13 additions & 0 deletions derive/src/lib.rs
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Expand Up @@ -184,6 +184,19 @@
//!
//! where `e`, `e1`, and `e2` are expressions.
//!
//! Matching is greedy, without backtracking. Note the difference in behavior for
//! these two rules in matching identifiers that don't end in an underscore:
//!
//! ```ignore
//! // input: ab_bb_b
//!
//! identifier = @{ "a" ~ ("b"|"_")* ~ "b" }
//! // matches: a b_bb_b nothing -> error!
//!
//! identifier = @{ "a" ~ ("_"* ~ "b")* }
//! // matches: a b, _bb, _b in three repetitions
//! ```
//!
//! Expressions can modify the stack only if they match the input. For example,
//! if `e1` in the compound expression `e1 | e2` does not match the input, then
//! it does not modify the stack, so `e2` sees the stack in the same state as
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13 changes: 13 additions & 0 deletions pest/src/lib.rs
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Expand Up @@ -197,6 +197,19 @@
//!
//! where `e`, `e1`, and `e2` are expressions.
//!
//! Matching is greedy, without backtracking. Note the difference in behavior for
//! these two rules in matching identifiers that don't end in an underscore:
//!
//! ```ignore
//! // input: ab_bb_b
//!
//! identifier = @{ "a" ~ ("b"|"_")* ~ "b" }
//! // matches: a b_bb_b nothing -> error!
//!
//! identifier = @{ "a" ~ ("_"* ~ "b")* }
//! // matches: a b, _bb, _b in three repetitions
//! ```
//!
//! Expressions can modify the stack only if they match the input. For example,
//! if `e1` in the compound expression `e1 | e2` does not match the input, then
//! it does not modify the stack, so `e2` sees the stack in the same state as
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