Implement selectable date formats for d

2 files changed, 81 insertions, 37 deletions

diff --git a/example.t b/example.t
index 78a3879..2fc9bd1 100644
--- a/example.t
+++ b/example.t
@@ -30,14 +30,13 @@
 ..
 .ec
 .
-.
 . \" start document
 .t
 .x Mg ,
 a simple macro package for troff
-.d \&
-John Ankarstr\(:om
 .d
+John Ankarstr\(:om
+.d e
 .
 .
 .h
@@ -252,8 +251,7 @@ There is a large group of macros that provide
 block-level formatting:
 .n 1
 .c d ,
-centered date (or given string, or nothing, if given
-.c \\\\& )
+centered date or text
 .n
 .c h ,
 heading
@@ -279,15 +277,27 @@ to create a centered header:
 .l
 \&.t
 Document title
-\&.d \\&
+\&.d
 First author
-\&.d \\&
+\&.br
 Second author
-\&.d \\" current date
+\&.d i \\" current date formatted as YYYY-MM-DD
 .p
-Here, you can see that the
+In the example above, you can see that the
+.c d
+macro may be used for other things than just dates.
+This works because
 .c d
-macro may be used for other things than dates.
+displays the date only if given
+an argument describing the desired date format:
+.n 1 a )
+.c i :
+international date, like
+.q 2021-06-21
+.n
+.c e :
+English date, like
+.q "21 June 2021"
 .
 .s
 Other macros
@@ -295,40 +305,48 @@ Other macros
 Finally, there are a few macros
 that belong to neither category:
 .n 1
+.ne 2
 .c ( ,
 begin footnote
 .n
 .c ) ,
 end footnote
 .n
+.ne 2
 .c q ,
 quotation
 .n
 .c w ,
 want space
 .p
-The footnote macros
+The macros
 .c (
 and
 .c )
-are used like this\c
-.(
-Note that
+create footnotes,
+placing a numerical reference at the place of their invocation.
+Both
 .c (
 and
 .c )
 take an optional argument,
-which is output immediately before or after
-the footnote number.
-.) :
+which is output either immediately before or immediately after
+the inline reference.
+For example, the following code
 .l
-\&.p
-A line of text\\c
+\&.q
+This is a quotation\\c
 \&.(
-.ne 2
-A footnote.
+This is a footnote.
 \&.) .
 .p
+creates the following reference:
+.q
+This is a quotation\c
+.(
+This is a footnote.
+.) .
+.p
 .i Mg
 does not account for cases where a footnote, because of its height,
 pushes the place where it is referenced to the next page.
@@ -352,22 +370,23 @@ This is an inline
 .p
 The
 .c w
-macro is a wrapper around troff's
-.c ne ,
+macro is an alternative to troff's
+.c ne
+request,
 which ensures that a given amount of space is available on the page
-\(em otherwise, a line break is issued \(em
+\(en otherwise, a line break is issued \(en
 but unlike
 .c ne ,
 which takes an exact amount of space as its argument,
 .c w
 takes a declarative specification
-describing the amount of space desired
+describing the amount of desired space
 in terms of
 .i mg
 environments.
 For example:
 .l
-\\" want space for...
+\&.\\" want space for...
 \&.w s p \\" a subheading of one line + a paragraph of one line
 \&.w s pp \\" a subheading of one line + a paragraph of two lines
 \&.w ss p \\" a subheading of two lines + a paragraph of one line
@@ -379,12 +398,12 @@ Internal macros
 .i Mg 's
 internal macros are generally not meant to be used outside of
 .i g.tmac .
-The group of macros controlling the environment \(en
+The environment-related macros
 .c (e ,
 .c @e
 and
 .c @c
-\(en are excepted from this rule,
+are, however, excepted from this rule,
 as it may be desirable to define custom environments
 for advanced documents.
 .p
@@ -395,6 +414,7 @@ is nothing more than a wrapper around troff's built-in
 but it may eventually be redefined in order to offer
 compatibility with implementations of troff
 without support for named environments.
+.p
 .c @e
 and
 .c @c
@@ -402,7 +422,10 @@ are equivalent to troff's
 .c ev
 and
 .c evc ,
-but keep track of a few extra variables (see
+but perform some extra work to keep track of
+.i mg 's
+special environment variables
+(see
 .i Environments
 above).
 .p
diff --git a/g.tmac b/g.tmac
index 917a0ba..8475988 100644
--- a/g.tmac
+++ b/g.tmac
@@ -279,16 +279,37 @@ ___________________
 .\" Environment macros -------------------------
 .
 .
-.\" d -- date
+.\" d -- centered date
 .de d
 . br
 . @e d
-. af mo 00
-. af dy 00
-. ie '\$1'' \n[year]-\n(mo-\n(dy
-. el .if !'\$1'\&' \$1
-. af mo 1
-. af dy 1
+.
+. \" international format
+. ie '\$1'i' \{\
+.  af mo 00
+.  af dy 00
+\n[year]-\n(mo-\n(dy
+.  af mo 1
+.  af dy 1
+. \}
+.
+. \" english format
+. el .if '\$1'e' \{\
+\n(dy
+. ie \n(mo=1 January
+. el .ie \n(mo=2 February
+. el .ie \n(mo=3 March
+. el .ie \n(mo=4 April
+. el .ie \n(mo=5 May
+. el .ie \n(mo=6 June
+. el .ie \n(mo=7 July
+. el .ie \n(mo=8 August
+. el .ie \n(mo=9 September
+. el .ie \n(mo=10 October
+. el .ie \n(mo=11 November
+. el December
+\n[year]
+. \}
 ..
 .\" h -- heading
 .de h
@@ -317,7 +338,7 @@ ___________________
 . @e s
 ..
 .
-.\" t -- title
+.\" t -- centered title
 .de t
 . br
 . @e t