Graphs.xtlm

1⍝│ Graphs: its macro library -- g_raph<, a graph written by its names.
2⍝│ Imported with the functions, under one alias: "g:" u_se< "Graphs".
3⍝│ A macro is a function from the source text written left and right of
4⍝│ its call to the source that replaces the call, run before the program
5⍝│ is compiled (X_eTaL MC10). Names with m: are macros; those under h: are
6⍝│ private to this file.
7
8"t:" u̲se< "Strings"
9"pa:" u̲se< "Parsing"
10
11⍝━━ Parsing
12
13⍝│ The lists of a list joined into one list.
14ʰr̲aze ← { b → d̲isclose '{ e̲nclose (d̲isclose ⍺) c̲at d̲isclose ⍵ } r̲/ b }
15
16⍝│ The paths of a graph text: a list per path, its stations in order,
17⍝│ cut at the commas and dashes outside brackets (Parsing's pa:s_plit,
18⍝│ as any list here is).
19ʰp̲aths ← { t → '{ p → '{ s → ᵗt̲rim d̲isclose s } m̲ap "-" ᵖᵃs̲plit ᵗt̲rim d̲isclose p } m̲ap "," ᵖᵃs̲plit t }
20
21⍝━━ The macro
22
23⍝│ "town" g:g_raph< "airport-bridge-center, center-docks": the graph
24⍝│ written by its names, paths of stations joined by "-", paths
25⍝│ separated by ",". When the program is compiled it defines a variable
26⍝│ per station, numbered in order of first appearance (airport := 1,
27⍝│ bridge := 2, ...), and town as the adjacency matrix, every edge both
28⍝│ ways, so the rest of the program speaks of stations by name
29⍝│ (town g:l_evels center). It stands as a statement of its own. A name
30⍝│ that cannot be a variable stops the compiler at it: error[bad-name].
31⍝│ takes: text text
32⍝│ uses: parsed
33ᵐg̲raph< ← { name t →
34  ps ← ʰp̲aths t
35  stations ← u̲nique ʰr̲aze ps
36  n̲ot ᵖᵃn̲ame? name ? "bad-name left" ⎕R̲EJECT name c̲at " cannot be a variable's name: a lowercase letter, then letters and digits"
37  bad ← (n̲ot '{ ᵖᵃn̲ame? d̲isclose ⍵ } e̲ach stations) r̲eplicate stations
38  0 < t̲ally bad ? "bad-name right" ⎕R̲EJECT (d̲isclose f̲irst bad) c̲at " cannot be a station's name: a lowercase letter, then letters and digits"
39  n ← t̲ally stations
40  ⍝ each station's number, path by path; neighbors on a path are edges
41  ks ← '{ p → stations i̲ndexOf d̲isclose p } m̲ap ps
42  a ← ʰr̲aze '{ k → -1 d̲rop d̲isclose k } m̲ap ks
43  b ← ʰr̲aze '{ k → 1 d̲rop d̲isclose k } m̲ap ks
44  from ← a c̲at b                              ⍝ both ways
45  to ← b c̲at a
46  at ← (n × from − 1) + to
47  m ← (r̲ange n × n) m̲ember? at
48  defs ← "\n" ᵗj̲oin '{ i → (d̲isclose i s̲elect stations) c̲at " := " c̲at f̲ormat i } m̲ap r̲ange n
49  defs c̲at "\n" c̲at name c̲at " := " c̲at (f̲ormat n) c̲at " " c̲at (f̲ormat n) c̲at " r_eshape " c̲at f̲ormat 0 + m
50}