Add 1994 Coroutine module by Tim Peters

Demo/threads/squasher.py

@@ -0,0 +1,104 @@
+# Coroutine example:  general coroutine transfers
+#
+# The program is a variation of a Simula 67 program due to Dahl & Hoare,
+# who in turn credit the original example to Conway.
+#
+# We have a number of input lines, terminated by a 0 byte.  The problem
+# is to squash them together into output lines containing 72 characters
+# each.  A semicolon must be added between input lines.  Runs of blanks
+# and tabs in input lines must be squashed into single blanks.
+# Occurrences of "**" in input lines must be replaced by "^".
+#
+# Here's a test case:
+
+test = """\
+   d    =   sqrt(b**2  -  4*a*c)
+twoa    =   2*a
+   L    =   -b/twoa
+   R    =   d/twoa
+  A1    =   L + R
+  A2    =   L - R\0
+"""
+
+# The program should print:
+
+# d = sqrt(b^2 - 4*a*c);twoa = 2*a; L = -b/twoa; R = d/twoa; A1 = L + R;
+#A2 = L - R
+#done
+
+# getline: delivers the next input line to its invoker
+# disassembler: grabs input lines from getline, and delivers them one
+#    character at a time to squasher, also inserting a semicolon into
+#    the stream between lines
+# squasher:  grabs characters from disassembler and passes them on to
+#    assembler, first replacing "**" with "^" and squashing runs of
+#    whitespace
+# assembler: grabs characters from squasher and packs them into lines
+#    with 72 character each, delivering each such line to putline;
+#    when it sees a null byte, passes the last line to putline and
+#    then kills all the coroutines
+# putline: grabs lines from assembler, and just prints them
+
+from Coroutine import *
+
+def getline(text):
+    for line in string.splitfields(text, '\n'):
+        co.back(line)
+
+def disassembler():
+    while 1:
+        card = co.tran(cogetline)
+        for i in range(len(card)):
+            co.tran(cosquasher, card[i])
+        co.tran(cosquasher, ';')
+
+def squasher():
+    while 1:
+        ch = co.tran(codisassembler)
+        if ch == '*':
+            ch2 = co.tran(codisassembler)
+            if ch2 == '*':
+                ch = '^'
+            else:
+                co.tran(coassembler, ch)
+                ch = ch2
+        if ch in ' \t':
+            while 1:
+                ch2 = co.tran(codisassembler)
+                if ch2 not in ' \t':
+                    break
+            co.tran(coassembler, ' ')
+            ch = ch2
+        co.tran(coassembler, ch)
+
+def assembler():
+    line = ''
+    while 1:
+        ch = co.tran(cosquasher)
+        if ch == '\0':
+            break
+        if len(line) == 72:
+            co.tran(coputline, line)
+            line = ''
+        line = line + ch
+    line = line + ' ' * (72 - len(line))
+    co.tran(coputline, line)
+    co.kill()
+
+def putline():
+    while 1:
+        line = co.tran(coassembler)
+        print line
+
+import string
+co = Coroutine()
+cogetline = co.create(getline, test)
+coputline = co.create(putline)
+coassembler = co.create(assembler)
+codisassembler = co.create(disassembler)
+cosquasher = co.create(squasher)
+
+co.tran(coputline)
+print 'done'
+
+# end of example