Remove unused code

RIP, beautiful and overflow-aware binary search. This code became dead
after we switched from lpeglabel to recursive descent.

src/pallene/Location.lua

@@ -5,54 +5,6 @@
 
 local util = require "pallene.util"
 
--- @param xs An ordered sequence of comparable items
--- @param v A value comparable to the items in the list
--- @return The position of the first occurrence of `v` in the sequence or the
--- position of the first item greater than `v` in the sequence, otherwise.
--- Inserting `v` at the returned position will always keep the sequence ordered.
-local function binary_search(xs, v)
-    -- Invariants:
-    --   1 <= lo <= hi <= #xs + 1
-    --   xs[i] < v , if i < lo
-    --   xs[i] >= v, if i >= hi
-    local lo = 1
-    local hi = #xs + 1
-    while lo < hi do
-        -- Average, rounded down (lo <= mid < hi)
-        -- Lua's logical right shift works here even if the addition overflows
-        local mid = (lo + hi) >> 1
-        if xs[mid] < v then
-            lo = mid + 1
-        else
-            hi = mid
-        end
-    end
-    return lo
-end
-
-local newline_cache = setmetatable({}, { __mode = "k" })
-
--- Converts an Lpeg file position into more familiar line and column numbers.
---
--- @param subject The contents of an entire source code file
--- @param pos A position in this file, as an absolute integer index
--- @return The line and column number at the specified position.
-local function get_line_number(subject, pos)
-    local new_lines
-    if newline_cache[subject] then
-        new_lines = newline_cache[subject]
-    else
-        new_lines = {}
-        for n in subject:gmatch("()\n") do
-            table.insert(new_lines, n)
-        end
-        newline_cache[subject] = new_lines
-    end
-    local line = binary_search(new_lines, pos)
-    local col  = pos - (new_lines[line - 1] or 0)
-    return line, col
-end
-
 --
 -- A datattype representing a point in a source code file
 --
@@ -65,11 +17,6 @@ function Location:init(file_name, line, col, pos)
     self.pos = pos
 end
 
-function Location.from_pos(file_name, source, pos) -- alternate constructor
-    local line, col = get_line_number(source, pos)
-    return Location.new(file_name, line, col, pos)
-end
-
 function Location:show_line()
     return string.format("%s:%d", self.file_name, self.line)
 end