elseif arithop == '*' then
factor = tonumber(factor)
if factor == nil then
error('Invalid default expression', 0)
end
value = value * factor
end
limit = tonumber(limit)
if limit == nil then
error('Invalid default expression', 0)
end
if compop == '<' then
return value < limit
elseif compop == '<=' then
return value <= limit
elseif compop == '>' then
return value > limit
elseif compop == '>=' then
return value >= limit
end
error('Invalid default expression', 0) -- should not occur
end
local lhs, rhs = condition:match('^(.-%W)and(%W.*)')
if lhs == nil then
return compare(value, condition)
end
return compare(value, lhs) and compare(value, rhs)
end  
local function get_default(value, unit_table)
-- Return true, s where s = name of unit's default output unit,
-- or return false, t where t is an error message table.
-- Some units have a default that depends on the input value
-- (the first value if a range of values is used).
-- If '!' is in the default, the first bang-delimited field is an
-- expression that uses 'v' to represent the input value.
-- Example: 'v < 120 ! small ! big ! suffix' (suffix is optional)
-- evaluates 'v < 120' as a boolean with result
-- 'smallsuffix' if (value < 120), or 'bigsuffix' otherwise.
-- Input must use en digits and '.' decimal mark.
local default = data_code.default_exceptions[unit_table.defkey or unit_table.symbol] or unit_table.default
if not default then
local per = unit_table.per
if per then
local function a_default(v, u)
local success, ucode = get_default(v, u)
if not success then
return '?' -- an unlikely error has occurred; will cause lookup of default to fail
end
-- Attempt to use only the first unit if a combination or output multiple.
-- This is not bulletproof but should work for most cases.
-- Where it does not work, the convert will need to specify the wanted output unit.
local t = all_units[ucode]
if t then
local combo = t.combination
if combo then
-- For a multiple like ftin, the "first" unit (ft) is last in the combination.
local i = t.multiple and table_len(combo) or 1
ucode = combo[i]
end
else
-- Try for an automatically generated combination.
local item = ucode:match('^(.-)%+') or ucode:match('^(%S+)%s')
if all_units[item] then
return item
end
end
return ucode
end
local unit1, unit2 = per[1], per[2]
local def1 = (unit1 and a_default(value, unit1) or unit_table.vprefix or '')
local def2 = a_default(1, unit2) -- 1 because per unit of denominator
return true, def1 .. '/' .. def2
end
return false, { 'cvt_no_default', unit_table.symbol }
end
if default:find('!', 1, true) == nil then
return true, default
end
local t = split(default, '!')
if #t == 3 or #t == 4 then
local success, result = pcall(evaluate_condition, value, t[1])
if success then
default = result and t[2] or t[3]
if #t == 4 then
default = default .. t[4]
end
return true, default
end
end
return false, { 'cvt_bad_default', unit_table.symbol }
end  
local linked_pages -- to record linked pages so will not link to the same page more than once  
local function unlink(unit_table)
-- Forget that the given unit has previously been linked (if it has).
-- That is needed when processing a range of inputs or outputs when an id
-- for the first range value may have been evaluated, but only an id for
-- the last value is displayed, and that id may need to be linked.
linked_pages[unit_table.unitcode or unit_table] = nil
end  
local function make_link(link, id, unit_table)
-- Return wikilink "id", possibly abbreviated as in examples:
-- mile --> mile
-- miles --> miles
-- However, just id is returned if:
-- * no link given (so caller does not need to check if a link was defined); or
-- * link has previously been used during the current convert (to avoid overlinking).
local link_key
if unit_table then
link_key = unit_table.unitcode or unit_table
else
link_key = link
end
if not link or link == '' or linked_pages[link_key] then
return id
end
linked_pages[link_key] = true
-- Following only works for language en, but it should be safe on other wikis,
-- and overhead of doing it generally does not seem worthwhile.
local l = link:sub(1, 1):lower .. link:sub(2)
if link == id or l == id then
return * .. id .. *
elseif link .. 's' == id or l .. 's' == id then
return '' .. id:sub(1, -2) .. 's'
else
return * .. id .. *
end
end  
local function variable_name(clean, unit_table)
-- For slwiki, a unit name depends on the value.
-- Parameter clean is the unsigned rounded value in en digits, as a string.
-- Value Source Example for "m"
-- integer 1: name1 meter (also is the name of the unit)
-- integer 2: var{1} metra
-- integer 3 and 4: var{2} metri
-- integer else: var{3} metrov (0 and 5 or more)
-- real/fraction: var{4} metra
-- var{i} means the i'th field in unit_table.varname if it exists and has
-- an i'th field, otherwise name2.
-- Fields are separated with "!" and are not empty.
-- A field for a unit using an SI prefix has the prefix name inserted,
-- replacing '#' if found, or before the field otherwise.
local vname
if clean == '1' then
vname = unit_table.name1
elseif unit_table.varname then
local i
if clean == '2' then
i = 1
elseif clean == '3' or clean == '4' then
i = 2
elseif clean:find('.', 1, true) then
i = 4
else
i = 3
end
if i > 1 and varname == 'pl' then
i = i - 1
end
vname = split(unit_table.varname, '!')[i]
end
if vname then
local si_name = rawget(unit_table, 'si_name') or ''
local pos = vname:find('#', 1, true)
if pos then
vname = vname:sub(1, pos - 1) .. si_name .. vname:sub(pos + 1)
else
vname = si_name .. vname
end
return vname
end
return unit_table.name2
end  
local function linked_id(parms, unit_table, key_id, want_link, clean)
-- Return final unit id (symbol or name), optionally with a wikilink,
-- and update unit_table.sep if required.
-- key_id is one of: 'symbol', 'sym_us', 'name1', 'name1_us', 'name2', 'name2_us'.
local abbr_on = (key_id == 'symbol' or key_id == 'sym_us')
if abbr_on and want_link then
local symlink = rawget(unit_table, 'symlink')
if symlink then
return symlink -- for exceptions that have the linked symbol built-in
end
end
local multiplier = rawget(unit_table, 'multiplier')
local per = unit_table.per
if per then
local paren1, paren2 = *, * -- possible parentheses around bottom unit
local unit1 = per[1] -- top unit_table, or nil
local unit2 = per[2] -- bottom unit_table
if abbr_on then
if not unit1 then
unit_table.sep = '' -- no separator in "$2/acre"
end
if not want_link then
local symbol = unit_table.symbol_raw
if symbol then
return symbol -- for exceptions that have the symbol built-in
end
end
if (unit2.symbol):find('⋅', 1, true) then
paren1, paren2 = '(', ')'
end
end
local key_id2 -- unit2 is always singular
if key_id == 'name2' then
key_id2 = 'name1'
elseif key_id == 'name2_us' then
key_id2 = 'name1_us'
else
key_id2 = key_id
end
local result
if abbr_on then
result = '/'
elseif omitsep then
result = per_word
elseif unit1 then
result = ' ' .. per_word .. ' '
else
result = per_word .. ' '
end
if want_link and unit_table.link then
if abbr_on or not varname then
result = (unit1 and linked_id(parms, unit1, key_id, false, clean) or '') .. result .. linked_id(parms, unit2, key_id2, false, '1')
else
result = (unit1 and variable_name(clean, unit1) or '') .. result .. variable_name('1', unit2)
end
if omit_separator(result) then
unit_table.sep = ''
end
return make_link(unit_table.link, result, unit_table)
end
if unit1 then
result = linked_id(parms, unit1, key_id, want_link, clean) .. result
if unit1.sep then
unit_table.sep = unit1.sep
end
elseif omitsep then
unit_table.sep = ''
end
return result .. paren1 .. linked_id(parms, unit2, key_id2, want_link, '1') .. paren2
end
if multiplier then
-- A multiplier (like "100" in "100km") forces the unit to be plural.
multiplier = from_en(multiplier)
if not omitsep then
multiplier = multiplier .. (abbr_on and '&nbsp;' or ' ')
end
if not abbr_on then
if key_id == 'name1' then
key_id = 'name2'
elseif key_id == 'name1_us' then
key_id = 'name2_us'
end
end
else
multiplier = ''
end