第９話 前判断と後判断の違い
を実現するプログラム例
Do While文の場合
Function f1(m As Long, n As Long, h As Long)
Dim w As Long, i As Long
i = m
While w + i <= n
w = w + i
i = i + h
Wend
f1 = w
End Function
Function f2(m As Long, n As Long, h As Long)
Dim w As Long, i As Long
i = m
While w + i * i <= n
w = w + i * i
i = i + h
Wend
f2 = w
End Function
Function f3(m As Long, n As Long, h As Long)
Dim w As Long, i As Long
i = m
While w + i * i * i <= n
w = w + i * i * i
i = i + h
Wend
f3 = w
End Function
Function f4(m As Long, n As Long, h As Long)
Dim w As Long, i As Long
i = m
While w + i * i * i * i <= n
w = w + i * i * i * i
i = i + h
Wend
f4 = w
End Function
Do...Loop While文の場合
Function f1(m As Long, n As Long, h As Long)
Dim w As Long, i As Long
i = m
While w + i <= n
w = w + i
i = i + h
Wend
f1 = w
End Function
Function f2(m As Long, n As Long, h As Long)
Dim w As Long, i As Long
i = m
While w + i * i <= n
w = w + i * i
i = i + h
Wend
f2 = w
End Function
Function f3(m As Long, n As Long, h As Long)
Dim w As Long, i As Long
i = m
While w + i * i * i <= n
w = w + i * i * i
i = i + h
Wend
f3 = w
End Function
Function f4(m As Long, n As Long, h As Long)
Dim w As Long, i As Long
i = m
While w + i * i * i * i <= n
w = w + i * i * i * i
i = i + h
Wend
f4 = w
End Function
解説
結局、今回の場合は前判断、後判断は関係ありませんでした。
判定条件 w + i <= n 等の問題にすぎなかったのです。
前判断と後判断の違いは、
最初の条件が偽であった場合に、
前判断は１回もループ処理が行われないのに対して、
後判断は偽でも１回はループ処理が行われることに、
にすぎないのです。
