Add Depth First Search in M4 (#5125)

Author: rzuckerm

archive/m/m4/depth-first-search.m4

@@ -0,0 +1,165 @@
+divert(-1)
+define(`show_usage',
+`Usage: please provide a tree in an adjacency matrix form 'dnl
+`("0, 1, 1, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0") 'dnl
+`together with a list of vertex values ("1, 3, 5, 2, 4") and the integer to find ("4")
+m4exit(`1')')
+
+dnl Reference: https://www.gnu.org/software/m4/manual/m4.html#index-array
+dnl array_get(varname, idx)
+define(`array_get', `defn(format(``%s[%s]'', `$1', `$2'))')
+
+dnl array_set(varname, idx, value)
+define(`array_set', `define(format(``%s[%s]'', `$1', `$2'), `$3')')
+
+dnl 2D versions of "array_get" and "array_set"
+dnl array2_get(varname, idx1, idx2)
+define(`array2_get', `defn(format(``%s[%s][%s]'', `$1', `$2', `$3'))')
+
+dnl array2_set(varname, idx1, idx2, value)
+define(`array2_set', `define(format(``%s[%s][%s]'', `$1', `$2', `$3'), `$4')')
+
+dnl is_valid(n)
+define(`is_valid', `eval(regexp(`$1', `^\s*-?[0-9]+\s*$') >= 0)')
+
+dnl parse_int_list(varname, args):
+dnl   varname["length"] = 0
+dnl   foreach arg in args:
+dnl     if not is_valid(arg):
+dnl       Return 0
+dnl     varname[varname["length"]] = arg
+dnl     varname["length"] = varname["length"] + 1
+dnl   Return 1
+define(`parse_int_list',
+`array_set(`$1', `length', 0)dnl
+_parse_int_list(`$1', $2)'dnl
+)
+define(`_parse_int_list',
+`ifelse(is_valid(`$2'), 0, `0',
+`array_set(`$1', array_get(`$1', `length'), `$2')dnl
+array_set(`$1', `length', incr(array_get(`$1', `length')))dnl
+ifelse(eval($# > 2), 1, `_parse_int_list(`$1', shift(shift($@)))', `1')'dnl
+)'dnl
+)
+
+dnl create_graph(conn_mtx_varname, vert_varname, graph_varname):
+dnl   // Create nodes
+dnl   graph_varname["length"] = vert_varname["length"]
+dnl   for i = 0 to conn_vert["length"] - 1:
+dnl     graph_varname[i]["value"] = vert_varname[i]
+dnl     graph_varname[i]["length"] = 0
+dnl
+dnl   // Connect children to nodes
+dnl   idx = 0
+dnl   for i = 0 to vert_varname["length"] - 1:
+dnl     for j = 0 to vert_varname["length"] - 1:
+dnl       if conn_mtx_varname[idx] > 0:
+dnl         graph_varname[i][graph_varname[i]["length"]] = j
+dnl         graph_varname[i]["length"] = graph_varname[i]["length"] + 1
+dnl
+dnl     idx = idx + 1
+define(`create_graph',
+`array_set(`$3', `length', array_get(`$2', `length'))dnl
+_create_nodes(`$2', `$3', 0)dnl
+_connect_children(`$1', `$2', `$3', 0, 0)dnl
+'dnl
+)
+
+dnl vert_varname=$1, graph_varname=$2, i=$3
+define(`_create_nodes',
+`ifelse(eval($3 < array_get(`$1', `length')), 1,
+`array2_set(`$2', `$3', `value', array_get(`$1', `$3'))dnl
+array2_set(`$2', `$3', `length', 0)dnl
+_create_nodes(`$1', `$2', incr($3))'dnl
+)'dnl
+)
+
+dnl conn_mtx_varname=$1, vert_varname=$2, graph_varname=$3, i=$4, idx=$5
+define(`_connect_children',
+`ifelse(eval($4 < array_get(`$2', `length')), 1,
+`_connect_children_inner(`$1', `$2', `$3', `$4', `$5', 0)dnl
+_connect_children(`$1', `$2', `$3', incr($4), eval($5 + array_get(`$2', `length')))'dnl
+)'dnl
+)
+
+dnl conn_mtx_varname=$1, vert_varname=$2, graph_varname=$3, i=$4, idx=$5, j=$6
+define(`_connect_children_inner',
+`ifelse(eval($6 < array_get(`$2', `length')), 1,
+`ifelse(eval(array_get(`$1', $5) + 0 > 0), 1,
+`array2_set(`$3', `$4', array2_get(`$3', `$4', `length'), `$6')dnl
+array2_set(`$3', `$4', `length', incr(array2_get(`$3', `$4', `length')))'dnl
+)dnl
+_connect_children_inner(`$1', `$2', `$3', `$4', incr($5), incr($6))'dnl
+)'dnl
+)
+
+dnl depth_first_search(graph_varname, target):
+dnl   // Indicate nothing visited
+dnl   visited = ""
+dnl
+dnl   // Indicate node not found
+dnl   found_node = -1
+dnl
+dnl   // Start depth first search at root (node 0)
+dnl   depth_first_search_rec(graph_varname, target, 0)
+dnl
+dnl  return found_node
+define(`depth_first_search',
+`pushdef(`visited', `')dnl
+pushdef(`found_node', `-1')dnl
+depth_first_search_rec(`$1', `$2', 0)dnl
+popdef(`visited')dnl
+found_node`'dnl
+popdef(`found_node')'dnl
+)
+
+dnl depth_first_search_rec(graph_varname, target, node):
+dnl   // Note: visited is a string that looks like this: "|<node1>||<node2>|..."
+dnl   // Since M4 does not have anything like a set, this is the easiest way to
+dnl   // represent it, and the "index" function can be used to see if a node has
+dnl   // been visited (negative if not visited)
+dnl
+dnl   // If target value found, indicate node found
+dnl   if graph_varname[node]["value"] == target:
+dnl     found_node = node
+dnl   else:
+dnl     // Indicate node is visited
+dnl     visited = visited + "|" + node + "|"
+dnl
+dnl     // For each child node
+dnl     for i = 0 to graph_varname[node]["length"] - 1
+dnl       // If child node not visited
+dnl       if "|" + graph_varname[node][i] + "|" not in visited:
+dnl         // Recursively check this child node
+dnl         depth_first_search_rec(graph_varname, target, graph_varname[node][i])
+dnl
+dnl         // Exit loop if node found
+dnl         if found_node >= 0:
+dnl           break
+define(`depth_first_search_rec',
+`ifelse(eval(array2_get(`$1', `$3', `value') == $2), 1,
+`define(`found_node', `$3')',
+`define(`visited', visited`|$3|')dnl
+_depth_first_search_rec(`$1', `$2', `$3', 0)'dnl
+)'dnl
+)
+
+dnl graph_varname=$1, target=$2, node=$3, i=$4
+define(`_depth_first_search_rec',
+`ifelse(eval(found_node < 0 && $4 < array2_get(`$1', `$3', `length')), 1,
+`ifelse(eval(index(visited, `|'array2_get(`$1', `$3', `$4')`|') < 0), 1,
+`depth_first_search_rec(`$1', `$2', array2_get(`$1', `$3', `$4'))'dnl
+)dnl
+_depth_first_search_rec(`$1', `$2', `$3', incr($4))'dnl
+)'dnl
+)
+
+divert(0)dnl
+ifelse(eval(ARGC < 3 || 
+    !parse_int_list(`conn_mtx', ARGV1) ||
+    !parse_int_list(`vert', ARGV2) ||
+    !is_valid(ARGV3)
+), 1, `show_usage()')dnl
+create_graph(`conn_mtx', `vert', `graph')dnl
+define(`node', depth_first_search(`graph', ARGV3))dnl
+ifelse(eval(node >= 0), 1, `true', `false')