Subranges and Ord in Delphi

A TLane = 1..4 subrange indexes an array of lap times, and Ord round-trips a letter.

program SubrangeOrd;
type
  TLane = 1..4;              // a subrange narrows a type's valid values
var
  Splits: array[TLane] of Integer;
  Lane: TLane;
  Grade: Char;
begin
  for Lane := Low(Splits) to High(Splits) do  // a subrange indexes arrays
    Splits[Lane] := 60 + Lane;
  WriteLn('lane 3 swam ', Splits[3], ' seconds');
  Grade := 'b';
  // Ord reads a character's code and Chr turns the code back.
  WriteLn(Grade, ' is code ', Ord(Grade), ', back to ', Chr(Ord(Grade)));
end.

How it works

1. TLane = 1..4; narrows the values, and Splits: array[TLane] of Integer indexes by it.
2. for Lane := Low(Splits) to High(Splits) do walks the subrange from end to end.
3. Ord(Grade) gives the code for 'b', and Chr(Ord(Grade)) turns it back.

Keywords and builtins used here

• Char
• Chr
• High
• Integer
• Low
• Ord
• WriteLn
• array
• begin
• do
• end
• for
• of
• program
• to
• type
• var

The run, in numbers

Lines

15

Characters to type

465

Tokens

106

Three-star pace

75 tpm

At the three-star pace of 75 tokens a minute, this run takes about 85 seconds.

Type this snippet

Step 3 of 3 in Enums & sets, step 18 of 27 in Language basics.

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