Conditions.jl

help?> @handler_case
 Convenience macro around handler_bind which works similar to try-catch, i.e., the first matching handler is run with the stack unwound and its result is returned.
 Examples
 ≡≡≡≡≡≡≡≡≡≡
 julia> @handler_case @signal(3.0) begin
 Integer => c -> (:integer, c)
 Number => c -> (:number, c)
 Any => c -> (:any, c)
 end
 (:number, 3.0)
 See also @signal, handler_bind as well as nonlocal and jump.

using Conditions
toggle_interactive(true)
h(z) = @signal z
g(y) = h(y + 2)
f(x) = g(2 * x)
f(3)
# Try @trace and @locals from the infiltration prompt! 

using Conditions
function nonneg(x::Number)
 if x >= 0
 x
 else
 @signal ArgumentError("Negative $x")
 end
end
function validate(x::Number)
 @restart_case nonneg(x) begin
 :fix_value => newval -> newval
 end
end
function mysum(xs::AbstractVector)
 @restart_case sum(validate, xs) begin
 :rough_guess => () -> 42
 end
end
# Restart functions
function fix_value(condition)
 fixme = find_restart(:fix_value)
 if !isnothing(fixme)
 fixval = 2
 println("Fixing $(condition.msg) into $fixval")
 invoke_restart(fixme, fixval)
 end
end
function rough_guess(condition)
 guess = find_restart(:rough_guess)
 if !isnothing(guess)
 println("Guessing total after $condition")
 invoke_restart(guess)
 end
end
xs = [1, 2, -1, 3, 4, -5, 0]
# Top-level handler decides what to do
handler_bind(Handler(ArgumentError, fix_value)) do
 mysum(xs)
end
handler_bind(Handler(ArgumentError, rough_guess)) do
 mysum(xs)
end