2 Other Markup
  
  
  2.1 Various types of text
  
  [→ B.5]
  
  In  this  section we present examples for all the various types of text that
  are possible in GAPDoc:
  
      This is emphasized.
  
      Keywords are typeset like this and that.
  
      Arguments of functions have an element. They look like this: x and y.
  
      Code   can   be  written  with  the  Code  element:  if  x  =  y  then
        Print("Equal"); fi; or while true do Print("Hello"); od;.
  
      Filenames    have   their   own   element:   /usr/local/ca/gap4r2   or
        pkg/xgap/doc.
  
      Buttons,  menus,  menu entries, and such things are also supported: OK
        or Cancel.
  
      Packages are typeset like this: Small Groups Library
  
      Quoted text: This is a text in quotes.
  
  Paragraphs are separated by the empty Par or P element.
  
  Alternatives  for different output formats: This is other than LaTeX output,
  namely: Text output.
  
  There are also three elements to typeset verbatim-like text. (→ B.6)
  
  The first is a Listing:
  
    GAP code  
    Sieve := function(n)
      # Returns the primes less than n
      local l,p,i;
      l := [1..n]; Unbind(l[1]);
      p := 2;
      while p^2 <= n do
          if IsBound(l[p]) then
              i := 2 * p;
              while i <= n do Unbind(l[i]); i := i + p; od;
          fi;
          p := p + 1;
      od;
      return Compacted(l);
    end;
  
  
  Here is a Log of a GAP session using this function:
  
    Example  
    gap> Sieve(100);
    [ 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61,
      67, 71, 73, 79, 83, 89, 97 ]
    gap> Length(last);
    25
  
  
  Here is a GAP Example session that is automatically tested:
  
    Example  
    gap> s := Size(CharacterTable("M"));
    808017424794512875886459904961710757005754368000000000
    gap> s < 10^53;                     
    false
    gap> s < 10^54;
    true
  
  
  
  2.2 Formulae
  
  [→ B.7]
  
  There are three types of formulae.
  
  The  first  is  the  normal math mode of LaTeX: b_i \cdot b_j = \sum_{k=1}^d
  h_{ijk} b_k. Then there are displayed formulae:
  
  
  \Longrightarrow    \quad    \left(\sum_{i=1}^d   x_i   b_i   \right)   \cdot
  \left(\sum_{j=1}^d  y_j b_j \right) = \sum_{k=1}^d \left( \sum_{i,j} x_i y_j
  h_{ijk} \right) b_k
  
  
  
  If  possible,  use the Alt element to specify a better readable text version
  of such a formula as in the following example:
  
           d                d                 d   
         -----            -----             -----  -----                 
          \                \                 \      \                    
   ==> (   )  x_i b_i )(    )  y_j b_j ) =    )  (   )  x_i y_j h_ijk ) b_k
          /                /                 /      /                    
         -----            -----             -----  -----                
         i = 1            j = 1             k = 1   i,j                
  
  For  small formulae without difficult parts use the M element: b_i, x^2, x^2
  +  2x  + 1 = (x + 1)^2. Note that here whitespace matters for text (or HTML)
  output.
  
  Here  are  two  formulae  containing  less than characters which are special
  characters for XML: a < b < c < d and e < f.
  
  Using the Mode attribute of a Display element formulae like
  
  
  a ⟶ a mod m'
  
  can also be displayed nicely in text and HTML output.
  
  
  2.3 Crossreferencing
  
  [→ B.8]
  
  In this section we demonstrate various references to parts of this document.
  Here  is a reference to this section: 2.3. Here is a reference to chapter 1,
  to appendix A, and to subsection 1.1-1.
  
  We  distinguish  among  others  references  to functions (see f (1.2-1)), to
  methods  with  tricky  name (see \^\{\}\[\]\<\& (1.2-2)), to operations (see
  MyOperation  (1.2-3)),  to  methods  (see MyOperation (1.2-4) or MyOperation
  (1.2-5)),  to  filters  (see  IsBla  (1.2-7)),  to  properties  (see IsBlubb
  (1.2-8)),  to attributes (see NumberBlobbs (1.2-9)), to variables (AllBlibbs
  (1.2-10)), to families (see BlibbsFamily (1.2-11)), and to info classes (see
  InfoBlibbs (1.2-12)).
  
  There  are  also references to labels: see 2.3, to other books: see 'GAPDoc:
  What  is  a DTD?' or IsSubgroup (Reference: IsSubgroup) in the GAP reference
  manual.
  
  References to sections come in two styles: 1 or 'Sectioning Elements'.
  
  Another  type  of  cross  referencing  is  bibliography. Here is a citation:
  [CR81, (5.22)] is an interesting lemma.
  
  There are also URLs:
  
  https://www.math.rwth-aachen.de/
  
  Email         addresses         have        a        special        element:
  mailto:Frank.Luebeck@Math.RWTH-Aachen.De
  
  and Homepages another one: https://www.math.rwth-aachen.de/~Frank.Luebeck/
  
  And      here      is      a      link      to     the     EDIM     archives
  (https://www.math.rwth-aachen.de/~Frank.Luebeck/gap/EDIM/index.html#ARCHS).
  
  One  can generate index entries as follows (look up the words TeX-UserGroup,
  RWTH, Aachen, Hauptbahnhof, and GAPDoc, for GAP programmers).
  
  
  2.4 Lists and Tables
  
  [→ B.9]
  
  There are
  
      lists
  
      enumerations, and
  
      tables
  
  or:
  
  1   lists
  
  2   enumerations, and
  
  3   tables
  
  or with marks:
  
  lists:
        not numbered
  
  enumerations:
        numbered
  
  tables:
        two-dimensional
  
  Lists can also be nested:
  
  1   1   first item of inner enumeration
  
        2   second item of inner enumeration
  
  2       first item of inner list
  
            second item of inner list
  
  Here is a table:
  
      ┌────────┬───────┬───────────┐
      │ Object │ Price │ available │ 
      ├────────┼───────┼───────────┤
      ├────────┼───────┼───────────┤
      │   Shoe │ $1,00 │ there     │ 
      ├────────┼───────┼───────────┤
      │    Hat │ $2,00 │ not there │ 
      └────────┴───────┴───────────┘
  
       Table: Prices
  
  
  
  2.5 Entities and Special Characters
  
  [→ B.10]
  
  Here is a table of special characters, the first two are special for XML and
  must  be  typed in by entities in GAPDoc documents. The other characters are
  special for LaTeX but in GAPDoc they can be typed directly.
  
      ┌───┬───┬───┬───┬───┬───┬───┬───┬───┬───┬───┬───┬───┐
      │ & │ < │ > │ # │ $ │ % │ ~ │ \ │ { │ } │ _ │ ^ │   │ 
      └───┴───┴───┴───┴───┴───┴───┴───┴───┴───┴───┴───┴───┘
  
       Table: Special characters in character data
  
  
  And here are the predefined entities in GAPDoc:
  
      ┌─────────────┬─────────┐
      │ &GAP;       │ GAP     │ 
      ├─────────────┼─────────┤
      │ &GAPDoc;    │ GAPDoc  │ 
      ├─────────────┼─────────┤
      │ &TeX;       │ TeX     │ 
      ├─────────────┼─────────┤
      │ &LaTeX;     │ LaTeX   │ 
      ├─────────────┼─────────┤
      │ &BibTeX;    │ BibTeX  │ 
      ├─────────────┼─────────┤
      │ &MeatAxe;   │ MeatAxe │ 
      ├─────────────┼─────────┤
      │ &XGAP;      │ XGAP    │ 
      ├─────────────┼─────────┤
      │ &copyright; │ ©       │ 
      └─────────────┴─────────┘
  
       Table: Predefined Entities in the GAPDoc system
  
  
  And some more for mathematical symbols: ℂ, ℤ, ℕ, ℙ, ℚ, ℍ, ℝ.