Forall Examples

FORALL is more versatile than array assignment:

• can access unusual sections,

  FORALL (i=1:n) A(i,i) = B(i)  ! diagonal
  DO j = 1, n 
   FORALL (i=1:j) A(i,j) = B(i) ! triangular
  END DO

• can use indices in RHS expression,

  FORALL (i=1:n,j=1:n,i/=j) A(i,j) = REAL(i+j)

• can call PURE procedures,

  FORALL (i=1:n:3,j=1:n:5) A(i,j) = SIN(A(j,i))

• can use indirection (vector subscripting),

  FORALL (i=1:n,j=1:n) A(VS(i),j) = i+VS(j)

The above are very difficult to express in Fortran 90.

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