2020-01-15 19:13:00

1 files changed, 242 insertions, 0 deletions

diff --git a/tex/context/base/mkiv/syst-lua.lua b/tex/context/base/mkiv/syst-lua.lua
index a63c49e8f..5911d7f00 100644
--- a/tex/context/base/mkiv/syst-lua.lua
+++ b/tex/context/base/mkiv/syst-lua.lua
@@ -156,3 +156,245 @@ implement {
         end
     end
 }
+
+-- This is a bit of a joke as I never really needed floating point expressions (okay,
+-- maybe only with scaling because there one can get numbers that are too large for
+-- dimensions to deal with). Of course one can write a parser in \TEX\ speak but then
+-- one also needs to implement a bunch of functions. It doesn't pay of so we just
+-- stick to the next gimmick. It looks inefficient but performance is actually quite
+-- efficient.
+
+local concat = table.concat
+local utfchar = utf.char
+local load, type, tonumber = load, type, tonumber
+
+local xmath    = xmath    or math
+local xcomplex = xcomplex or { }
+
+local cmd          = tokens.commands
+
+local get_next     = token.get_next
+local get_command  = token.get_command
+local get_mode     = token.get_mode
+local get_index    = token.get_index
+local get_csname   = token.get_csname
+local get_macro    = token.get_macro
+
+local put_next     = token.put_next
+
+local scan_token   = token.scan_token
+
+local getdimen     = tex.getdimen
+local getglue      = tex.getglue
+local getcount     = tex.getcount
+local gettoks      = tex.gettoks
+local gettex       = tex.get
+
+local context      = context
+local dimenfactors = number.dimenfactors
+
+local result = { "return " }
+local word   = { }
+local r      = 1
+local w      = 0
+
+local report = logs.reporter("system","expression")
+
+local function unexpected(c)
+    report("unexpected token %a",c)
+end
+
+local function expression()
+    local w = 0
+    local r = 1
+    while true do
+        local t = get_next()
+        local n = get_command(t)
+        local c = cmd[n]
+        -- todo, helper: returns number
+        if c == "letter"  then
+            w = w + 1 ; word[w] = utfchar(get_mode(t))
+        else
+            if w > 0 then
+                local s = concat(word,"",1,w)
+                local d = dimenfactors[s]
+                if d then
+                    r = r + 1 ; result[r] = "*"
+                    r = r + 1 ; result[r] = 1/d
+                else
+                    if xmath[s] then
+                        r = r + 1 ; result[r] = "xmath."
+                    elseif xcomplex[s] then
+                        r = r + 1 ; result[r] = "xcomplex."
+                    end
+                    r = r + 1 ; result[r] = s
+                end
+                w = 0
+            end
+            if     c == "other_char" then
+                r = r + 1 ; result[r] = utfchar(get_mode(t))
+            elseif c == "spacer" then
+             -- r = r + 1 ; result[r] = " "
+            elseif c == "relax" then
+                break
+            elseif c == "assign_int" then
+                r = r + 1 ; result[r] = getcount(get_index(t))
+            elseif c == "assign_dimen" then
+                r = r + 1 ; result[r] = getdimen(get_index(t))
+            elseif c == "assign_glue" then
+                r = r + 1 ; result[r] = getglue(get_index(t))
+            elseif c == "assign_toks" then
+                r = r + 1 ; result[r] = gettoks(get_index(t))
+            elseif c == "char_given" or c == "math_given" or c == "xmath_given" then
+                r = r + 1 ; result[r] = get_mode(t)
+            elseif c == "last_item" then
+                local n = get_csname(t)
+                if n then
+                    local s = gettex(n)
+                    if s then
+                        r = r + 1 ; result[r] = s
+                    else
+                        unexpected(c)
+                    end
+                else
+                    unexpected(c)
+                end
+            elseif c == "call" then
+                local n = get_csname(t)
+                if n then
+                    local s = get_macro(n)
+                    if s then
+                        r = r + 1 ; result[r] = s
+                    else
+                        unexpected(c)
+                    end
+                else
+                    unexpected(c)
+                end
+            elseif c == "the" or c == "convert" or c == "lua_expandable_call" then
+                put_next(t)
+                scan_token() -- expands
+            else
+                unexpected(c)
+            end
+        end
+    end
+    local code = concat(result,"",1,r)
+    local func = load(code)
+    if type(func) == "function" then
+        context(func())
+    else
+        report("invalid lua %a",code)
+    end
+end
+
+-- local letter_code              <const> = cmd.letter
+-- local other_char_code          <const> = cmd.other_char
+-- local spacer_code              <const> = cmd.spacer
+-- local other_char_code          <const> = cmd.other_char
+-- local relax_code               <const> = cmd.relax
+-- local assign_int_code          <const> = cmd.assign_int
+-- local assign_dimen_code        <const> = cmd.assign_dimen
+-- local assign_glue_code         <const> = cmd.assign_glue
+-- local assign_toks_code         <const> = cmd.assign_toks
+-- local char_given_code          <const> = cmd.char_given
+-- local math_given_code          <const> = cmd.math_given
+-- local xmath_given_code         <const> = cmd.xmath_given
+-- local last_item_code           <const> = cmd.last_item
+-- local call_code                <const> = cmd.call
+-- local the_code                 <const> = cmd.the
+-- local convert_code             <const> = cmd.convert
+-- local lua_expandable_call_code <const> = cmd.lua_expandable_call
+--
+-- local function unexpected(c)
+--     report("unexpected token %a",c)
+-- end
+--
+-- local function expression()
+--     local w = 0
+--     local r = 1
+--     while true do
+--         local t = get_next()
+--         local n = get_command(t)
+--         if n == letter_code  then
+--             w = w + 1 ; word[w] = utfchar(get_mode(t))
+--         else
+--             if w > 0 then
+--                 -- we could use a metatable for all math, complex and factors
+--                 local s = concat(word,"",1,w)
+--                 local d = dimenfactors[s]
+--                 if d then
+--                     r = r + 1 ; result[r] = "*"
+--                     r = r + 1 ; result[r] = 1/d
+--                 else
+--                     if xmath[s] then
+--                         r = r + 1 ; result[r] = "xmath."
+--                     elseif xcomplex[s] then
+--                         r = r + 1 ; result[r] = "xcomplex."
+--                     end
+--                     r = r + 1 ; result[r] = s
+--                 end
+--                 w = 0
+--             end
+--             if     n == other_char_code then
+--                 r = r + 1 ; result[r] = utfchar(get_mode(t))
+--             elseif n == spacer_code then
+--              -- r = r + 1 ; result[r] = " "
+--             elseif n == relax_code then
+--                 break
+--             elseif n == assign_int_code then
+--                 r = r + 1 ; result[r] = getcount(get_index(t))
+--             elseif n == assign_dimen_code then
+--                 r = r + 1 ; result[r] = getdimen(get_index(t))
+--             elseif n == assign_glue_code then
+--                 r = r + 1 ; result[r] = getglue(get_index(t))
+--             elseif n == assign_toks_code then
+--                 r = r + 1 ; result[r] = gettoks(get_index(t))
+--             elseif n == char_given_code or n == math_given_code or n == xmath_given_code then
+--                 r = r + 1 ; result[r] = get_mode(t)
+--             elseif n == last_item_code then
+--                 local n = get_csname(t)
+--                 if n then
+--                     local s = gettex(n)
+--                     if s then
+--                         r = r + 1 ; result[r] = s
+--                     else
+--                         unexpected(c)
+--                     end
+--                 else
+--                     unexpected(c)
+--                 end
+--             elseif n == call_code then
+--                 local n = get_csname(t)
+--                 if n then
+--                     local s = get_macro(n)
+--                     if s then
+--                         r = r + 1 ; result[r] = s
+--                     else
+--                         unexpected(c)
+--                     end
+--                 else
+--                     unexpected(c)
+--                 end
+--             elseif n == the_code or n == convert_code or n == lua_expandable_call_code then
+--                 put_next(t)
+--                 scan_token() -- expands
+--             else
+--                 unexpected(c)
+--             end
+--         end
+--     end
+--     local code = concat(result,"",1,r)
+--     local func = load(code)
+--     if type(func) == "function" then
+--         context(func())
+--     else
+--         report("invalid lua %a",code)
+--     end
+-- end
+
+implement {
+    public  = true,
+    name    = "expression",
+    actions = expression,
+}