The RESHAPE Intrinsic Function

RESHAPE is a general intrinsic function which delivers an array of a specified shape:

 
    RESHAPE(SOURCE,SHAPE[,PAD][,ORDER])

Note,

• the RESHAPE intrinsic changes the shape of SOURCE to the specified SHAPE.
• SOURCE must be intrinsic typed array, it cannot be an array of user-defined types.
• SHAPE is a one dimensional array specifying the target shape. It is convenient to use an explicit array constructor for this field in order to make things clearer.
• PAD is a one dimensional array of values which is used to pad out the resulting array if there are not enough values in SOURCE. The PAD constructor is used repeatedly (in array element order) to provide enough elements for the result. PAD is optional.
• ORDER allows the dimensions to be permuted, in other words, allows the array element ordering to be modified, ORDER is optional.

For example, the following statement assigns SOURCE to A,

    A = RESHAPE((/1,2,3,4/),(/2,2/))

The result of the RESHAPE is a array (specified by the second argument (/2,2/)), the result is filled in array element order and looks like:

    1  3
    2  4

Also consider

    A = RESHAPE((/1,2,3,4/),(/2,2/),&
                     ORDER=(/2,1/))

This time the array is filled up in row major form, (the subscripts of dimension 2 vary the quickest,) this is specified by the ORDER=(/2,1/) specifier. The default ordering is, of course, ORDER=(/1,2/). The ORDER keyword is necessary because some optional arguments are missing. A looks like

    1  2
    3  4

Visualisation,

 
Figure: Visualisation of the Effect of the RESHAPE Intrinsic

Clearly the result of RESHAPE must conform to the array object on the LHS of the =, consider,

    RESHAPE((/1,2,3,4,5,6/),(/2,4/),(/0/),(/2,1/))

this has the value

    1  2  3  4
    5  6  0  0

The source object has less elements that the LHS so the resulting array is padded with the extra values taken repeatedly from the third array argument, PAD, (/0/). Note how this reference does not use keyword arguments, it is directly equivalent to,

    RESHAPE(SOURCE=(/1,2,3,4,5,6/),&
             SHAPE=(/2,4/),        &
               PAD=(/0/),          &
             ORDER=(/2,1/))

and

    RESHAPE(SOURCE=(/1,2,3,4,5,6/),&
               PAD=(/0/),          &
             SHAPE=(/2,4/),        &
             ORDER=(/2,1/))

If one of the optional arguments is absent then keyword arguments should be used for the other optional argument to make it clear to the compiler (and the user) which is the missing argument. The keywords are the names of the dummy arguments.

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