エラー処理記述の面倒さ
Error handling codes
記述が面倒
Usually complicated
本質(calc)の記述がエラー処理に埋没
Important part (calc func) hidden in many error handling codes
if(条件1) ....
if(条件2) ....
result = calc()
if(例外発生) ...
if(結果NG) ...