54 lines
1.6 KiB
Lua
Executable File
54 lines
1.6 KiB
Lua
Executable File
--------------------------------------------------------------------------------
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--
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-- Scopes: this library helps keeping track of identifier scopes,
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-- typically in code walkers.
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--
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-- * scope:new() returns a new scope instance s
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--
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-- * s:push() bookmarks the current set of variables, so the it can be
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-- retrieved next time a s:pop() is performed.
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--
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-- * s:pop() retrieves the last state saved by s:push(). Calls to
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-- :push() and :pop() can be nested as deep as one wants.
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--
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-- * s:add(var_list, val) adds new variable names (stirng) into the
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-- scope, as keys. val is the (optional) value associated with them:
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-- it allows to attach arbitrary information to variables, e.g. the
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-- statement or expression that created them.
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--
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-- * s:push(var_list, val) is a shortcut for
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-- s:push(); s:add(var_list, val).
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--
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-- * s.current is the current scope, a table with variable names as
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-- keys and their associated value val (or 'true') as value.
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--
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--------------------------------------------------------------------------------
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scope = { }
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scope.__index = scope
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function scope:new()
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local ret = { current = { } }
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ret.stack = { ret.current }
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setmetatable (ret, self)
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return ret
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end
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function scope:push(...)
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table.insert (self.stack, table.shallow_copy (self.current))
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if ... then return self:add(...) end
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end
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function scope:pop()
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self.current = table.remove (self.stack)
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end
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function scope:add (vars, val)
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val = val or true
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for i, id in ipairs (vars) do
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assert(id.tag=='Id' or id.tag=='Dots' and i==#vars)
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if id.tag=='Id' then self.current[id[1]] = val end
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end
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end
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return scope |