pred is_whitespace(c: char) -> bool {
    const ch_space: char = '\u0020';
    const ch_ogham_space_mark: char = '\u1680';
    const ch_mongolian_vowel_sep: char = '\u180e';
    const ch_en_quad: char = '\u2000';
    const ch_em_quad: char = '\u2001';
    const ch_en_space: char = '\u2002';
    const ch_em_space: char = '\u2003';
    const ch_three_per_em_space: char = '\u2004';
    const ch_four_per_em_space: char = '\u2005';
    const ch_six_per_em_space: char = '\u2006';
    const ch_figure_space: char = '\u2007';
    const ch_punctuation_space: char = '\u2008';
    const ch_thin_space: char = '\u2009';
    const ch_hair_space: char = '\u200a';
    const ch_narrow_no_break_space: char = '\u202f';
    const ch_medium_mathematical_space: char = '\u205f';
    const ch_ideographic_space: char = '\u3000';
    const ch_line_separator: char = '\u2028';
    const ch_paragraph_separator: char = '\u2029';
    const ch_character_tabulation: char = '\u0009';
    const ch_line_feed: char = '\u000a';
    const ch_line_tabulation: char = '\u000b';
    const ch_form_feed: char = '\u000c';
    const ch_carriage_return: char = '\u000d';
    const ch_next_line: char = '\u0085';
    const ch_no_break_space: char = '\u00a0';

    if c == ch_space { true }
    else if c == ch_ogham_space_mark { true }
    else if c == ch_mongolian_vowel_sep { true }
    else if c == ch_en_quad { true }
    else if c == ch_em_quad { true }
    else if c == ch_en_space { true }
    else if c == ch_em_space { true }
    else if c == ch_three_per_em_space { true }
    else if c == ch_four_per_em_space { true }
    else if c == ch_six_per_em_space { true }
    else if c == ch_figure_space { true }
    else if c == ch_punctuation_space { true }
    else if c == ch_thin_space { true }
    else if c == ch_hair_space { true }
    else if c == ch_narrow_no_break_space { true }
    else if c == ch_medium_mathematical_space { true }
    else if c == ch_ideographic_space { true }
    else if c == ch_line_tabulation { true }
    else if c == ch_paragraph_separator { true }
    else if c == ch_character_tabulation { true }
    else if c == ch_line_feed { true }
    else if c == ch_line_tabulation { true }
    else if c == ch_form_feed { true }
    else if c == ch_carriage_return { true }
    else if c == ch_next_line { true }
    else if c == ch_no_break_space { true }
    else { false }
}