Overview
This lesson covers string manipulation in Delphi using built-in procedures (Part 2). Focus is on the Delete and Insert procedures, which directly modify string variables rather than creating new ones.
String Basics (Recap)
- A string contains text, numbers, and other characters all treated as text.
- Example: "Hello World" stored in variable
sTemp.
- Each character has a position (e.g., position 5 is "o", position 6 is a space).
- Procedures modify the original variable instead of returning a new value.
String Manipulation Procedures
| Procedure | Parameters | Description | Example Result |
|---|
| Delete | string, start_position, count | Removes specified number of characters starting from given position | Delete(sTemp, 3, 5) on "Hello World" → "He World" |
| Insert | substring, string, position | Inserts substring into string at specified position; shifts remaining characters | Insert("boy", sTemp, 6) on "Hello World" → "Hello boy World" |
Delete Procedure
- Takes three parameters: target string, starting position (integer), number of characters to delete (integer).
- Physically modifies the original string variable.
Delete(sTemp, 3, 2) starts at position 3 and removes 2 characters (positions 3 and 4).Delete(sTemp, 3, 5) removes positions 3 through 7 (five characters total).- If requested count exceeds available characters, deletes only what exists.
- Example:
Delete(sTemp, 9, 1000) on "Hello World" removes last three characters only.
- Result from
Delete(sTemp, 3, 5): "He orld" becomes "He World".
Insert Procedure
- Takes three parameters: substring to insert, target string, insertion position (integer).
- Modifies the second parameter (target string) by inserting the first parameter (substring).
- Shifts all characters from insertion point onwards; does not replace existing content.
Insert("boy", sTemp, 6) places "boy" at position 6, shifts remaining text right.- If position exceeds string length, substring appends to the end (no padding spaces).
- Example:
Insert("boy", sTemp, 1000) on "Hello World" results in "Hello World boy".
- Does not create gaps; simply extends the string at the farthest valid position.
Key Terms & Definitions
- Procedure: Called by name without assignment; modifies parameters directly rather than returning values.
- Parameter: Value passed to a procedure or function for processing.
- Substring: A portion of text intended for insertion into another string.
- Position: Integer representing character location within a string (1-indexed in Delphi).