Using Format Reversion

Programmer Guide > Format Strings > Using Format Reversion

If the data is all of the same type, you can abbreviate the C and FORTRAN format strings using the technique of format reversion. Format reversion is a shorthand way of specifying a format string.

For more information on format reversion with FORTRAN format strings, refer to a FORTRAN 77 handbook.

Example—Using Format Reversion to Write Integer Data

This example writes data to a file using a single C format string:

var1 = INDGEN(20)

status = DC_WRITE_FIXED("simple.dat", var1, Format="5%i")

Similarly, the entire file can be written with other PV-WAVE statements using the following FORTRAN format string:

OPENW, 1, "simple.dat"

var1 = INDGEN(20) +1

PRINTF, 1, var1, Format="(5(I4))"

CLOSE, 1

The abbreviated format strings repeatedly writes the integer values in var1 until all of the data has been transferred. The result is a data file, simple.dat, that contains 20 integer values:

1	2	3	4	5
6	7	8	9	10
11	12	13	14	15
16	17	18	19	20

Example—Using Format Reversion to Read Floating-Point Data

The following data file, tesla.dat, contains only floating point numbers:

.8945  .5768  .3958  .3098  .8948  .8495
.0938  .8749  .4798  .9204  .2479  .9485

This entire file can be read using a single C format string:

status = DC_READ_FIXED('tesla.dat', var1, Format="%f")

This abbreviated format string repeatedly reads or writes floating point numbers until all of the data are read or written.

Similarly, the entire file can be read with other PV-WAVE statements using the following FORTRAN format string:

OPENR, 1, "tesla.dat"

var1 = FLTARR(12)

READF, 1, var1, Format="(F5.4,2X)"

CLOSE, 1

This FORTRAN format string example assumes that there are two spaces between each value, as represented by the 2X.

Version 2017.1