rust-quiz:017-unary-decrement.rs

godme發表於2022-07-12
RustUIREM
系列文章：
rust-quiz:001-macro-count-statements.rs rust-quiz:002-bitand-or-reference.rs rust-quiz:003-mutate-const.rs rust-quiz:004-dotdot-in-tuple.rs rust-quiz:005-trait-resolution-hrtb.rs rust-quiz:006-value-of-assignment.rs rust-quiz:007-surprise-wildcard-match.rs rust-quiz:008-tokenize-punctuation.rs rust-quiz:009-opaque-metavariable.rs rust-quiz:010-shadowed-trait-object-method.rs rust-quiz:011-function-pointer-comparison.rs rust-quiz:012-binding-drop-behavior.rs rust-quiz:013-mutable-zst.rs rust-quiz:014-trait-autoref.rs rust-quiz:015-inference-of-number-type.rs rust-quiz:016-prefix-decrement.rs rust-quiz:017-unary-decrement.rs rust-quiz:018-method-or-function-pointer.rs rust-quiz:019-dropped-by-underscore.rs rust-quiz:020-break-return-in-condition.rs rust-quiz:021-closure-or-logical-or.rs rust-quiz:022-macro-tokenize-number.rs rust-quiz:023-inherent-vs-trait-method.md rust-quiz:024-local-and-const-hygiene.rs rust-quiz:025-unit-infallible-match.rs rust-quiz:026-iterator-lazy-map.rs rust-quiz:027-subtrait-dispatch.rs rust-quiz:028-underscore-prefix.rs rust-quiz:029-tuple-trailing-commas.rs rust-quiz:030-clone-pointers.rs rust-quiz:031-method-lookup.rs rust-quiz:032-or-pattern-guard.rs rust-quiz:033-range-full-method.rs 
fn main() {
    let mut a = 5;
    let mut b = 3;
    print!("{}", a-- - --b);
}

rust沒有++和--，都會被拆解為+和-。

a-- - --b=> a-(-(-(-(-b)))) => a - b
很簡單，有五個-，兩兩抵消，最後結果就是相減，結果為2

2

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