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authorJakob Kaivo <jkk@ung.org>2022-03-04 12:32:20 -0500
committerJakob Kaivo <jkk@ung.org>2022-03-04 12:32:20 -0500
commit55f277e77428d7423ae906a8e1f1324d35b07a7d (patch)
tree5c1c04703dff89c46b349025d2d3ec88ea9b3819 /miralib/manual/29.m
import Miranda 2.066 from upstream
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+> || _L_i_t_e_r_a_t_e_ _s_c_r_i_p_t_s_ _(_a_n_ _a_l_t_e_r_n_a_t_i_v_e_ _c_o_m_m_e_n_t_ _c_o_n_v_e_n_t_i_o_n_)
+
+The standard comment convention for Miranda scripts is that anything
+rightwards from a pair of vertical bars to the end of a line is taken to
+be comment and ignored by the compiler, thus
+ ||This is a comment
+
+Everything else in the script is taken to be formal program text. An
+inverted style of commenting is also available in Miranda, permitting
+the construction of a "literate script" (the name is taken from
+Professor Donald Knuth's idea of "literate programming"). In a literate
+script EVERYTHING is assumed to be comment, except for lines marked with
+the formalising symbol '>' in column 1. For example the following lines
+
+> fac 0 = 1
+> fac (n+1) = (n+1)*fac n
+
+would be taken as formal program text - and could be preceded and/or
+followed by some narrative explaining what the factorial function is and
+why we define it in this way.
+
+To minimise the danger that you will accidentally omit the '>" from one
+line of your formal text without the compiler noticing that something is
+wrong, the following additional rule applies to Miranda literate scripts
+- whenever a group of lines of formal program text is preceded or
+followed by some lines of "narrative", the two types of text must be
+separated by at least one blank line. You will see that this has been
+done for the definition of factorial given above. (Definition - a
+"blank line" is one containing only white space.)
+
+Within the formal sections of a literate script the standard comment
+convention still works. For example
+
+> result = sum [fac n | n <- [1..50]] ||NB this is a large number!
+
+The compiler takes a decision on which comment convention applies by
+looking at the first line of a script. If this has a '>' in column 1,
+then it is a literate script, otherwise the compiler assumes it is a
+conventional script. Typically the first line of a literate script will
+just be a comment, eg
+
+> ||This is a literate script
+
+In fact this manual section is a legal Miranda script, defining `fac'
+and `result' (see first line).
+
+An alternative convention is based on the name of the file - if this
+ends in `.lit.m' then it is assumed to be a literate script,
+independently of the form of the first line. This makes it possible to
+have literate scripts which begin in `narrative' mode.
+
+As an aid to maintaining good layout in literate scripts, a simple text
+formatting program, called `just' (short for justify), is supplied with
+the Miranda system. This leaves untouched the formal sections of the
+script and formats the narrative parts to specified width (default 72).
+
+There is a UNIX manual page for `just' which gives details of its
+behaviour. Note that `just' is a general purpose text formatting tool
+and is not in any way Miranda-specific.
+
+As an additional aid to the use of document preparation tools in
+conjunction with Miranda scripts, the Miranda compiler will recognise
+underlined keywords. This applies both to reserved words, such as `_d_i_v'
+and `_m_o_d' and to directives such as `_%_e_x_p_o_r_t' (underlining of the
+initial `%' is optional). The style of underlining accepted is
+`backspace-underline-character' as generated by nroff/troff. It will
+also recognise the underlined symbols _> and _< as being equivalent to >=,
+<= respectively. This works in both literate scripts and scripts using
+the standard comment convention.
+
+_U_s_i_n_g_ _L_a_T_e_X_ _w_i_t_h_ _M_i_r_a_n_d_a_ _l_i_t_e_r_a_t_e_ _s_c_r_i_p_t_s
+ Because of the `.lit.m' convention it is possible for a file to be both
+a Miranda script and a LaTeX source file. In such a case the sections
+of formal Miranda text (recognised by the Miranda compiler by the `>' in
+column 1) will be surrounded by the LaTeX commands
+ \begin{verbatim}
+
+ \end{verbatim}
+ A similar arrangement can be made for troff.
+
+[The 1989 distribution included a program, mtotex, for using mira with
+LaTeX, but this no longer works and has been removed - DT]
+
+_A_c_k_n_o_w_l_e_d_g_e_m_e_n_t_s
+ The '>' inverse-comment convention (and the "blank line" rule) are due
+to Richard Bird and Philip Wadler of Oxford University Programming
+Research Group, and were first used in their language "Orwell".
+