# Fibonacci数列的和式表达及wat实现

**Published by:** [Aulee](https://paragraph.com/@aulee/)
**Published on:** 2024-08-29
**URL:** https://paragraph.com/@aulee/fibonacci-wat

## Content

设数列的第$$n$$项为$$f(n)$$，则根据定义有$$f(n)=f(n-1)+f(n-2)$$。由此易得， $$f(n) = f(1) + f(0) + f(1) + … + f(n-2)$$ 用wat语言（wasm）可实现求和法计算$$f(n)$$如下：(module (func $fib (export "fib") (param $n i32) (result i32) (local $tmp i32) (local.set $tmp (i32.const 1)) (block $break (br_if $break (i32.lt_s (local.get $n) (i32.const 2))) (loop $loop (local.set $tmp (i32.add (call $fib (i32.add (local.get $n) (i32.const -2))) (local.get $tmp))) (br_if $loop (i32.gt_s (local.tee $n (i32.add (local.get $n) (i32.const -1))) (i32.const 1))) ) ) local.get $tmp ) ) 直接用f(n)=f(n-1)+f(n-2)的逻辑，wat代码为： (module (func $fib (export "fib") (param $n i32) (result i32) (local $tmp i32) (local.set $tmp (i32.const 1)) (block $break (br_if $break (i32.lt_s (local.get $n) (i32.const 2))) (local.set $tmp (i32.add (call $fib (i32.add (local.get $n) (i32.const -2))) (call $fib (i32.add (local.get $n) (i32.const -1))))) ) local.get $tmp ) )

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