[問題] 我實在看不出fortran compiler說的錯誤是什麼@@

[pianoboy (人還挺多的嘛)]

我檢查很多次了
但我實在看不出我錯在哪裡@@
請各位高手能夠指教一下><
唉~Fortran真是難搞....


***************Compiler出現的錯誤訊息*****************************

[chkao@linux3 ~]$ g77 0828.f
0828.f: In subroutine `trapz':
0828.f:24:
         if n = 1  then
         ^
Invalid form for IF statement at (^)
0828.f:24:
         if n = 1  then
         1
0828.f:26: (continued):
            else
            2
Statement at (2) invalid in context established by
statement at (1)
0828.f:24:
         if n = 1  then
         1
0828.f:32: (continued):
         END IF
         2
Statement at (2) invalid in context established by
statement at (1)


***************附上原程式^^***************************************


      program   calculus

      integer n , i
      real h,a,b
      double precision func,s,p
      a = 0
      b = 1.5
      p = 0
      write(*,*) 'choose the number you want to divide?'
      read(*,*)  n
      call trapz(n ,h,s,p,a,b)
      write(*,*) p
      end


      subroutine trapz(n ,h,s,p,a,b)

      integer n , i
      real h ,a,b
      double precision func,s,p

      if n = 1  then
         p = (func(a)+func(b))*(b-a)/2
         else
      do 100 i = 1 , n
         s = (func(a) + func(1.5/n*i))*(b-a)/n/2
         p = p + s

  100 continue
      END IF

      end


      double precision function  func(x)
      real x
      func = 0.84885406 + 31.51924706*x - 137.66731262*x**2
     - +240.55831238*x**3 - 171.45245361*x**4 + 41.95066071*x**5

      end



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