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Sub-string ([]) operator

Sub-string ([ ]) operator takes a character expression and returns a sub-string of this expression:

Description: Substring%20(%5b%5d)%20Operator

The operator takes one or two comma-separated parameters:

first is the integer number of the character in the string with which the sub-string must start, and
last is the integer number of the character in the string with which the sub-string must end.

If you specify only the first parameter, [ ] will return one single character.

For example, these code lines:

LET a = "Smith"

LET b = a[2]

DISPLAY b

will return m.

If you specify both first and last parameters, [ ] will return the character with the first number, the character with the last number, and all characters between them.

For example, these code lines:

LET a = "Smith"

LET b = a[2, 4]

DISPLAY b

will return mit.

first and last parameters must be greater than zero. first parameter must be in the range from 1 to length where length is the length of the character string. last must be no less than first and no greater than length.

Here is a simple example of how to use the sub-string ([ ]) operator:

MAIN

DEFINE a, b CHAR(5), c ARRAY [3, 4, 5] OF CHAR(5)

LET a = "Smith"

LET b = a[2, 4] -- mit

LET c[2, 2, 2] = a[3,4] -- it

DISPLAY "*** Sub-string Example ***" AT 1, 5

DISPLAY "LET a = \"Smith\"" AT 3, 5

DISPLAY "a: " ,a at 4, 5

DISPLAY "LET b = a[2, 4]" AT 6, 5

DISPLAY "b: " , b at 7, 5

DISPLAY "LET c[2, 2, 2] = a[3, 4]" AT 9, 5

DISPLAY "c: " , c[2, 2, 2] at 10, 5

CALL fgl_getkey()

END MAIN

Operands invalid for the sub-string ([ ]) operator

A parameter is invalid for the sub-string ([ ]) operator if

first is 0 or negative
first is larger than last
first or last cannot be converted to an integer value
last is greater than length
you try to get a sub-string from a CHAR or VARCHAR variable, ARRAY element, or RECORD member which declared size is smaller than last
you try to get a sub-string from an empty string

In Querix 4GL, invalid operands produce runtime error -1332. A character variable has referenced subscripts that are out of range.

In some locales, the sub-string ([ ]) operator is byte-based. In East Asian locales that support multi-byte characters, 4GL automatically replaces any partial characters that this operator attempts to create with single-byte white-space characters so that no partial character is returned.