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Go over table-semantics description yet again

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rocky
2017-10-03 05:42:14 -04:00
parent c8d15e7654
commit 86305097d2
2 changed files with 20 additions and 12 deletions
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3
uncompyle6/semantics/fragments.py
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@@ -1,6 +1,4 @@
# Copyright (c) 2015-2017 by Rocky Bernstein
# Copyright (c) 2005 by Dan Pascu <dan@windowmaker.org>
# Copyright (c) 2000-2002 by hartmut Goebel <h.goebel@crazy-compilers.com>
# Copyright (c) 1999 John Aycock
"""
@@ -94,7 +92,6 @@ TABLE_DIRECT_FRAGMENT = {
'importfrom': ( '%|from %[2]{pattr}%x import %c\n', (2, (0, 1)), 3),
'importmultiple': ( '%|import%b %c%c\n', 0, 2, 3 ),
'list_for': (' for %c%x in %c%c', 2, (2, (1, )), 0, 3 ),
'forstmt': ( '%|for%b %c%x in %c:\n%+%c%-\n\n', 0, 3, (3, (2, )), 1, 4 ),
'forelsestmt': (
'%|for %c%x in %c:\n%+%c%-%|else:\n%+%c%-\n\n', 3, (3, (2,)), 1, 4, -2),
'forelselaststmt': (

29
uncompyle6/semantics/pysource.py
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@@ -25,21 +25,28 @@ Python.
# of the nonterminal is suffixed with "_exit" it will be called after
# all of its children are called.
#
# However if this were done for all of the rules, this file would be even longer
# than it is already.
# After a while writing methods this way, you'll find many routines which do similar
# sorts of things, and soon you'll find you want a short notation to
# describe rules and not have to create methods at all.
#
# Another more compact way to specify a semantic rule for a nonterminal is via
# rule given in one of the tables MAP_R0, MAP_R, or MAP_DIRECT.
# So another other way to specify a semantic rule for a nonterminal is via
# one of the tables MAP_R0, MAP_R, or MAP_DIRECT where the key is the
# nonterminal name.
#
# These uses a printf-like syntax to direct substitution from attributes
# of the nonterminal and its children..
# These dictionaries use a printf-like syntax to direct substitution
# from attributes of the nonterminal and its children..
#
# The rest of the below describes how table-driven semantic actions work
# and gives a list of the format specifiers. The default() and
# template_engine() methods implement most of the below.
#
# Step 1 determines a table (T) and a path to a
# table key (K) from the node type (N) (other nodes are shown as O):
# We allow for a couple of ways to interact with a node in a tree. So
# step 1 after not seeing a custom method for a nonterminal is to
# determine from what point of view tree-wise the rule is applied.
# In the diagram below, "N" is a nonterminal name, and K is the table
# key name; we show where those are with respect to each other in the
# AST tree for N.
#
#
# N&K N N
# / | ... \ / | ... \ / | ... \
@@ -48,13 +55,17 @@ Python.
# K
# TABLE_DIRECT TABLE_R TABLE_R0
#
# The default is a "TABLE_DIRECT" mapping. The key K is then extracted from the
# The default is a "TABLE_DIRECT" mapping By far, most rules used work this way.
# TABLE_R0 is rarely used.
#
# The key K is then extracted from the
# subtree and used to find a table entry T[K], if any. The result is a
# format string and arguments (a la printf()) for the formatting engine.
# Escapes in the format string are:
#
# %c evaluate the node recursively. Its argument is a single
# integer representing a node index.
#
# %p like %c but sets the operator precedence.
# Its argument then is a tuple indicating the node
# index and the precidence value, an integer.