nomsu/core/errors.nom

#!/usr/bin/env nomsu -V1
#
    This file contains basic error reporting code

use "core/metaprogramming.nom"

compile [traceback] to: Lua value "debug.traceback()"
compile [traceback %] to: Lua value "debug.traceback('', \(% as lua expr))"
compile [barf] to: Lua "error(nil, 0);"
compile [barf %msg] to: Lua "error(\(%msg as lua expr), 0);"
compile [assume %condition] to
    lua> "local \%assumption = 'Assumption failed: '..tostring(nomsu:tree_to_nomsu(\%condition))"
    return
        Lua ".."
            if not \(%condition as lua expr) then
                error(\(quote "\%assumption"), 0)
            end

compile [assume %condition or barf %message] to
    Lua ".."
        if not \(%condition as lua expr) then
            error(\(%message as lua expr), 0)
        end

# Try/except
compile [..]
    try %action and if it succeeds %success or if it barfs %msg %fallback
    try %action and if it barfs %msg %fallback or if it succeeds %success
..to
    Lua ".."
        do
            local fell_through = false
            local err, erred = nil, false
            local ok, ret = xpcall(function()
                \(%action as lua statements)
                fell_through = true
            end, function(\(%msg as lua expr))
                local ok, ret = pcall(function()
                    \(%fallback as lua statements)
                end)
                if not ok then err, erred = ret, true end
            end)
            if ok then
                \(%success as lua statements)
                if not fell_through then
                    return ret
                end
            elseif erred then
                error(err, 0)
            end
        end

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
parse [..]
    try %action and if it succeeds %success or if it barfs %fallback
    try %action and if it barfs %fallback or if it succeeds %success
..as: try %action and if it succeeds %success or if it barfs (=lua "") %fallback
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
parse [try %action] as
    try %action and if it succeeds: do nothing
    ..or if it barfs: do nothing
parse [try %action and if it barfs %fallback] as
    try %action and if it succeeds: do nothing
    ..or if it barfs %fallback
parse [try %action and if it barfs %msg %fallback] as
    try %action and if it succeeds: do nothing
    ..or if it barfs %msg %fallback
parse [try %action and if it succeeds %success] as
    try %action and if it succeeds %success or if it barfs: do nothing