progress-4gl Strings String manipulation
Example
There are a couple of useful built in functions for working with string. All functions working with the position of characters start with index 1 as the first character, not 0 as is common in many languages.
STRING - converts any value to a string
This example converts the integer 2000 to the string "2000".
DEFINE VARIABLE i AS INTEGER NO-UNDO.
DEFINE VARIABLE c AS CHARACTER NO-UNDO.
i = 2000.
c = STRING(i).
DISPLAY c.
CHR and ASC - converts single characters to and from ascii.
CHR(integer)
Returns the character representation for ascii code integer
ASC(character)
Returns the ascii integer value for the character
DEFINE VARIABLE ix AS INTEGER NO-UNDO.
DEFINE VARIABLE letter AS CHARACTER NO-UNDO FORMAT "X(1)" EXTENT 26.
DO ix = 1 TO 26:
letter[ix] = CHR((ASC("A")) - 1 + ix).
END.
DISPLAY SKIP(1) letter WITH 2 COLUMNS NO-LABELS
TITLE "T H E A L P H A B E T".
LENGTH - returns the length of a string
LENGTH(string). //Returns an integer with the length of the string.
DEFINE VARIABLE cString AS CHARACTER NO-UNDO.
cString = "HELLO".
MESSAGE "The string " cString " is " LENGTH(cString) " characters long" VIEW-AS ALERT-BOX.
SUBSTRING - returns or assigns a part of a string
- SUBSTRING(string, starting-position, length).
Returns "length" characters from "string" starting on position "starting-position".
- SUBSTRING(string, starting-position).
Returns the rest of "string", starting at position "starting-position"
DEFINE VARIABLE cString AS CHARACTER NO-UNDO.
cString = "ABCDEFGH".
DISPLAY SUBSTRING(cString, 4, 2). //Displays "DE"
DISPLAY SUBSTRING(cString, 4). //Displays "DEFGH"
Substring can also be used to overwrite a part of a string. Use the same syntax but assign that substring instead:
DEFINE VARIABLE cString AS CHARACTER NO-UNDO.
cString = "ABCDEFGH".
SUBSTRING(cString, 4, 2) = "XY". //Replaces position 4 and 5 with "XY"
DISPLAY cString.
There's also a similar function called OVERLAY this example from the Progress documentation covers the differences between OVERLAYand SUBSTRING:
/* This procedure illustrates the differences between the SUBSTRING and
OVERLAY statements. */
DEFINE VARIABLE cOriginal AS CHARACTER NO-UNDO INITIAL "OpenEdge".
DEFINE VARIABLE cSubstring AS CHARACTER NO-UNDO.
DEFINE VARIABLE cOverlay AS CHARACTER NO-UNDO.
DEFINE VARIABLE cResults AS CHARACTER NO-UNDO.
/* Default behavior without optional LENGTH. */
ASSIGN
cSubstring = cOriginal
SUBSTRING(cSubstring,2) = "***"
cOverlay = cOriginal
OVERLAY(cOverlay,2) = "***"
cResults = "target = ~"OpenEdge~". ~n~n"
+ "If you do not supply a length, SUBSTRING and OVERLAY default as follows:
~n~n" + "SUBSTRING(target,2) = ~"***~" yields: " + cSubstring + ". ~n"
+ "OVERLAY(target,2) = ~"***~" yields: " + cOverlay + ".".
/* Behavior with zero LENGTH. */
ASSIGN
cSubstring = cOriginal
SUBSTRING(cSubstring,2,0) = "***"
cOverlay = cOriginal
OVERLAY(cOverlay,2,0) = "***"
cResults = cResults + "~n~n"
+ "For a zero length, SUBSTRING and OVERLAY behave as follows: ~n~n"
+ "SUBSTRING(target,2,0) = ~"***~" yields: " + cSubstring + ". ~n"
+ "OVERLAY(target,2,0) = ~"***~" yields: " + cOverlay + ".".
/* Behavior with LENGTH < replacement. */
ASSIGN
cSubstring = cOriginal
SUBSTRING(cSubstring,2,1) = "***"
cOverlay = cOriginal
OVERLAY(cOverlay,2,1) = "***"
cResults = cResults + "~n~n"
+ "For a length shorter than the replacement, SUBSTRING and OVERLAY behave
as follows: ~n~n" + "SUBSTRING(target,2,1) = ~"***~" yields: "
+ cSubstring + ". ~n" + "OVERLAY(target,2,1) = ~"***~" yields: "
+ cOverlay + ".".
/* Behavior with LENGTH = replacement. */
ASSIGN
cSubstring = cOriginal
SUBSTRING(cSubstring,2,3) = "***"
cOverlay = cOriginal
OVERLAY(cOverlay,2,3) = "***"
cResults = cResults + "~n~n"
+ "For a length equal to the replacement, SUBSTRING and OVERLAY behave as
follows: ~n~n" + "SUBSTRING(target,2,3) = ~"***~" yields: "
+ cSubstring + ". ~n" + "OVERLAY(target,2,3) = ~"***~" yields: "
+ cOverlay + ".".
/* Behavior with LENGTH > replacement. */
ASSIGN
cSubstring = cOriginal
SUBSTRING(cSubstring,2,6) = "***"
cOverlay = cOriginal
OVERLAY(cOverlay,2,6) = "***"
cResults = cResults + "~n~n"
+ "For a length greater than the replacement, SUBSTRING and OVERLAY behave
as follows: ~n~n" + "SUBSTRING(target,2,6) = ~"***~" yields: "
+ cSubstring + ". ~n" + "OVERLAY(target,2,6) = ~"***~" yields: "
+ cOverlay + ".".
MESSAGE cResults VIEW-AS ALERT-BOX.
INDEX - return the position of a string in a string.
R-INDEX will to the same thing but search right to left.
INDEX(source, target)
Search target within source (left to right) and return it's position. If it's missing return 0.
INDEX(source, target, starting-position).
Same as above but start searching at starting-position
DEFINE VARIABLE str AS CHARACTER NO-UNDO.
str = "ABCDEFGH".
DISPLAY INDEX(str, "cd") INDEX(str, "cd", 4). //Will display 3 and 0
REPLACE - replaces a string within a string.
REPLACE(string, from-string, to-string)
Replaces from-string with to-string in string. From-string and to-string don't need to be of the same length, to-string can also be nothing ("") to remove a character.
DEFINE VARIABLE c AS CHARACTER NO-UNDO.
c = "ELLO".
DISPLAY REPLACE(c, "E", "HE"). // Displays "HELLO"
c = "ABABABA".
DISPLAY REPLACE(c, "B", ""). // Remove all Bs
TRIM - removes leading and trailing whitespaces (or other characters).
This can be useful when cleaning up indata.
TRIM(string)
Removes all leading and trailing spaces, tabs, line feeds, carriage returns.
TRIM(string, character).
Removes all leading and trailing "characters".
LEFT-TRIM and RIGHT-TRIM does the same thing but only leading or trailing.
DEFINE VARIABLE c AS CHARACTER NO-UNDO.
c = "__HELLO_WORLD_____".
DISPLAY TRIM(c, "_").
/*Displays HELLO_WORLD without all the leading and
trailing underscores but leaves the one in the middle.
REPLACE would have removed that one as well */
SUBSTITUTE - substitutes paramters in a string.
SUBSTITUTE is a limited function for replacing up to nine preformatted parameters in a string.
SUBSTITUTE(string, param1, param2, ..., param9).
The parameters must be in the format &1 to &9.
If you want to use an ampersand in the string (and not use it as a parameter) escape it with another ampersand: &&.
DEFINE VARIABLE str AS CHARACTER NO-UNDO.
str = "&1 made &2 goals in &3 games playing for &4".
MESSAGE SUBSTITUTE(str, "Zlatan Ibrahimovic", 113, 122, "Paris Saint-Germain") VIEW-AS ALERT-BOX.
MESSAGE SUBSTITUTE(str, "Mats Sundin", 555, 1305, "Toronto Maple Leafs") VIEW-AS ALERT-BOX.
A parameter can appear more than once in a string, all will be replaced:
MESSAGE SUBSTITUTE("&1 &2 or not &1 &2", "To", "Be") VIEW-AS ALERT-BOX.
