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String::Fields - class for setting fixed size fields in a Str


    use String::Fields;

    my $sf := String::Fields.new(2,3,4)
    .say for $sf.set-string("abcdefghijklmnopqrstuvwxyz");
    # ab
    # cde
    # fghi

    my $sf := String::Fields.new(2 => 5, 8, 3);
    my $s = "012345678901234567890";

    $s.&apply-fields($sf);  # or: apply-fields($s,$sf)
    say $s;            # 012345678901234567890
    say $s[0];         # 23456
    say $s[1];         # 78901234
    say $s[2];         # 567
    say $s.join(":");  # 23456:78901234:567

    # one time application
    $s.&apply-fields(2,3,4);  # or: apply-fields($s,2,3,4)

    # using a literal string
    my @fields = "abcdefg".&apply-fields(2,3);  # ["ab","cde"]


String::Fields allows one to specify fixed length fields that can be applied to a string, effectively turning it into a sequence of strings that can be individually accessed or iterated over.

When the object is loaded with a string, it can be used as a string in all the normal ways that a string would.



my $sf := String::Fields.new(2,3,4)

The new method creates a new String::Fields object that contains the format information of the fields. It takes any number of arguments to indicate the position and width of the fields. If the argument consists of just a number, it means the width of a field from where the last field has ended (or from position 0 for the first argument). If the argument consists of a Pair, then the key is taken for the offset, and the value is taken to be the width.

Please note that this just sets the format information. This allows the same object to be used for different strings. Setting the string to be used, is either done with the set-string method, or by calling the apply-fields subroutine.



Joins all fields together with the given separator.



The set-string method sets the string to which the format information should be applied.



apply-fields($s,$sf);  # or $s.&apply-fields($sf)

# one time application
$s.&apply-fields(2,3,4);  # or: apply-fields($s,2,3,4)

# using a literal string
my @fields = "abcdefg".&apply-fields(2,3);  # ["ab","cde"]

If the first argument to the apply-fields subroutine is a variable with a string in it, then it will become a String::Fields object (but will still act as the original string). If it is a string literal, then the created / applied String::Fields object will be returned. The other arguments indicate the fields that should be applie. This can be either be a String::Fields object, or it can any number of field specifications, as can be passed to the new method.


Elizabeth Mattijsen liz@raku.rocks

Source can be located at: https://github.com/lizmat/String-Fields . Comments and Pull Requests are welcome.


Copyright 2020, 2021 Elizabeth Mattijsen

This library is free software; you can redistribute it and/or modify it under the Artistic License 2.0.