Data commit

Task/S-expressions/Lua/s-expressions-1.lua

@@ -0,0 +1,27 @@
+lpeg = require 'lpeg' -- see http://www.inf.puc-rio.br/~roberto/lpeg/
+
+imports = 'P R S C V match'
+for w in imports:gmatch('%a+') do _G[w] = lpeg[w] end -- make e.g. 'lpeg.P' function available as 'P'
+
+function tosymbol(s) return s end
+function tolist(x, ...) return {...} end -- ignore the first capture, the whole sexpr
+
+ws = S' \t\n'^0                 -- whitespace, 0 or more
+
+digits = R'09'^1                -- digits, 1 or more
+Tnumber = C(digits * (P'.' * digits)^-1) * ws / tonumber -- ^-1 => at most 1
+
+Tstring = C(P'"' * (P(1) - P'"')^0 * P'"') * ws
+
+sep = S'()" \t\n'
+symstart = (P(1) - (R'09' + sep))
+symchar = (P(1) - sep)
+Tsymbol = C(symstart * symchar^0) * ws / tosymbol
+
+atom = Tnumber + Tstring + Tsymbol
+lpar = P'(' * ws
+rpar = P')' * ws
+sexpr = P{ -- defines a recursive pattern
+    'S';
+    S = ws * lpar * C((atom + V'S')^0) * rpar / tolist
+}

Task/S-expressions/Lua/s-expressions-2.lua

@@ -0,0 +1,24 @@
+eg_input = [[
+((data "quoted data" 123 4.5)
+ (data (!@# (4.5) "(more" "data)")))
+]]
+
+eg_produced = match(sexpr, eg_input)
+
+eg_expected = { -- expected Lua data structure of the reader (lpeg.match)
+    {'data', '"quoted data"', 123, 4.5},
+    {'data', {'!@#', {4.5}, '"(more"', '"data)"'}}
+}
+
+function check(produced, expected)
+    assert(type(produced) == type(expected))
+    if type(expected) == 'table' then -- i.e. a list
+        assert(#produced == #expected)
+        for i = 1, #expected do check(produced[i], expected[i]) end
+    else
+        assert(produced == expected)
+    end
+end
+
+check(eg_produced, eg_expected)
+print("checks out!") -- won't get here if any <i>check()</i> assertion fails

Task/S-expressions/Lua/s-expressions-3.lua

@@ -0,0 +1,26 @@
+function pprint(expr, indent)
+    local function prindent(fmt, expr)
+        io.write(indent) -- no line break
+        print(string.format(fmt, expr))
+    end
+    if type(expr) == 'table' then
+        if #expr == 0 then
+            prindent('()')
+        else
+            prindent('(')
+            local indentmore = '  ' .. indent
+            for i= 1,#expr do pprint(expr[i], indentmore) end
+            prindent(')')
+        end
+    elseif type(expr) == 'string' then
+        if expr:sub(1,1) == '"' then
+            prindent("%q", expr:sub(2,-2)) -- print as a Lua string
+        else
+            prindent("%s", expr) -- print as a symbol
+        end
+    else
+        prindent("%s", expr)
+    end
+end
+
+pprint(eg_expected, '')