Command-code syntax


General command syntax:


column-reference

or

command-code  [  string-operand  ]  [  column-reference  |  numeric-operand  ]


Column-reference:

See paragraph 4 above for description.  A column reference by itself (without a command-code) selects one or more columns from the source string and appends them to the end of the result string.  


When a . dot precedes a column reference by itself, it selects one or more columns from the current value of the result string and appends them to the end of that result string.  When a column-reference appears on a modifying command, it always refers to the result string, whether a dot is used or not; the dot is implied in such cases.


A column reference following a command code usually selects a set of columns of the source string to be acted on by the command.  See the description of the specific command for details on what the column reference is used for.


Command-code:

One or more letters like L or TR, defining a mapping action to be performed.  Command codes for DD, DX, XD and XX allow an extended syntax; see paragraph 11 below.


String-operand:

An optional quoted string value, used by a command code.  This will generally have the same syntax as inserted-text does; see paragraph 7 above for more information.  See the description of the specific command for details on what this string operand may be used for.  Some commands allow the string operand to be specified as a pair; see paragraph 9 above for more information.  Certain commands will accept a string set or string pair as a string operand.


Numeric-operand:

An optional decimal value, used by some command codes, instead of a column reference.  For example, the Pad command code P uses the numeric operand to specify a single decimal value as the number of padding characters to be used.


For some commands, the string-operand and/or the column-reference may be either mandatory or disallowed.  See individual command descriptions for more information.



Extended command-code syntax for DD, DX, XD and XX   


The command codes DD, DX, XD and XX can be used in a “standard” syntax or in an “extended” syntax.  In standard syntax, the column reference operand selects the entire numeric field for numeric conversion and reformatting.


In extended syntax, the selected columns are scanned (left-to-right or right-to-left) for numeric digits delimited by non-digit characters.  In a given string that is selected, up to 9 numeric fields within it can be scanned for, using an ordinal number (the n value below ) of 1 through


The specific placement of the n value within the command code determines whether the scan goes left-to-right, or right-to-left.  When the n value is left of the first character of the command code (like 2DX), the scan goes left-to-right.  When the n value is right of the first character of the command code (like D2X), the scan goes right-to-left.  See the examples below.  (If the n value is specified as 0 it will be ignored.)


Once a value is found, you determine the width of the converted value you want to allow for (the w value below) and the type of value you want to producer (the t value below).



Using DX as an example, this command can appear as  nDXwt   or  DnXwt





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