Sub-string extraction: substr

Syntax

substr ( op, start, length )

Input parameters

op	the operand
start	the starting digit (first character) of the string to be extracted
length	the length (number of characters) of the string to be extracted

Examples of valid syntaxes

substr  ( DS_1,  2 ,  3 )
substr  ( DS_1, 2 )
substr  ( DS_1, _ , 3 )
substr  ( DS_1 )

Semantics for scalar operations

The operator extracts a substring from op, which must be string type. The substring starts from the startth character of the input string and has a number of characters equal to the length parameter.

If start is omitted, the substring starts from the 1st position.
If length is omitted or overcomes the length of the input string, the substring ends at the end of the input string.
If start is greater than the length of the input string, an empty string is extracted.

For example:

substr (“abcdefghijklmnopqrstuvwxyz”, 5 , 10 )  gives: “efghijklmn”
substr (“abcdefghijklmnopqrstuvwxyz”, 25 , 10 ) gives: “yz”
substr (“abcdefghijklmnopqrstuvwxyz”, 30 , 10 ) gives: “”

Input parameters type

op

dataset { measure<string> _+ }
| component<string>
| string

start

component < integer [ value >= 1 ] >
| integer [ value >= 1 ]

length

component < integer [ value >= 0 ] >
| integer [ value >= 0 ]

Result type

result

dataset { measure<string> _+ }
| component<string>
| string

Additional Constraints

None.

Behavior

As for the invocations at Data Set level, the operator has the behaviour of the “Operators applicable on one Scalar Value or Data Set or Data Set Component”. As for the invocations at Component or Scalar level, the operator has the behaviour of the “Operators applicable on more than two Scalar Values or Data Set Components” (see the section “Typical behaviours of the ML Operators”).

Examples

Given the operand datasets DS_1 and DS_2:

Input DS_1 (see structure)

Id_1	Id_2	Me_1	Me_2
1	A	hello world	medium size text
1	B	abcdefghilmno	short text
2	A	pqrstuvwxyz	this is a long description

Example 1

DS_r:= substr ( DS_1 , 7 );

results in (see structure):

DS_r
Id_1	Id_2	Me_1	Me_2
1	A	world	size text
1	B	ghilmno	text
2	A	vwxyz	s a long description

Example 2

DS_r:= substr ( DS_1 , 1 , 5 );

results in (see structure):

DS_r
Id_1	Id_2	Me_1	Me_2
1	A	hello	mediu
1	B	abcde	short
2	A	pqrst	this

Example 3

DS_r:= DS_1 [ calc Me_2:= substr ( Me_2 , 1 , 5 ) ];

results in (see structure):

DS_r
Id_1	Id_2	Me_1	Me_2
1	A	hello world	mediu
1	B	abcdefghilmno	short
2	A	pqrstuvwxyz	this