Allow a tolerance in check macro (#3)

Author: timholy

README.md

@@ -50,6 +50,11 @@ It then tests whether the result obtained from the "safe" arguments is consisten
 the result obtained from `a` and `b`.
 If the two differ to within the precision of the "ordinary" (unsafe) result, an
 error is thrown.
+Optionally, you can supply keywords accepted by `isapprox`:
+
+```julia
+@check foo(a) atol=1e-12
+```
 
 Packages can specialize `CheckedArithmetic.safearg` to control how `asafe` and `bsafe`
 are generated. To guard against oversights, `safearg` must be explicitly defined for

src/CheckedArithmetic.jl

@@ -99,20 +99,22 @@ macro checked(expr)
     return esc(replace_checked!(expr))
 end
 
-macro check(expr)
+macro check(expr, kws...)
     isexpr(expr, :call) || error("expected :call expression, got ",
                                  isa(expr, Expr) ? QuoteNode(expr.head) : typeof(expr))
     safeexpr = copy(expr)
     for i = 2:length(expr.args)
         safeexpr.args[i] = Expr(:call, :(CheckedArithmetic.safearg), expr.args[i])
     end
+    cmpexpr = isempty(kws) ? :(val == valcmp || error(val, " is not equal to ", valcmp)) :
+                             :(isapprox(val, valcmp; $(esc(kws...))) || error(val, " is not approximately equal to ", valcmp))
     return quote
         local val = $(esc(expr))
         local valcmp = CheckedArithmetic.safeconvert(typeof(val), $(esc(safeexpr)))
         if ismissing(val) && ismissing(valcmp)
             val
         else
-            val == valcmp || error(val, " is not equal to ", valcmp)
+            $cmpexpr
             val
         end
     end
@@ -147,6 +149,8 @@ safearg_type(::Type{Float32})  = Float64
 safearg_type(::Type{Float16})  = Float64
 safearg_type(::Type{T}) where T<:Base.TwicePrecision = T
 
+safearg_type(::Type{<:Rational}) = Float64
+
 """
     xsafe = CheckedArithmetic.safearg(x)
 

test/runtests.jl

@@ -70,6 +70,14 @@ end
                         now()]
             @test @check(identity(item)) === item
         end
+
+        # Roundoff error
+        function diff2from1(s)
+            s2 = copy(s + s)
+            return 1 - s2
+        end
+        @test_throws ErrorException @check diff2from1(1//3)
+        @test (@check diff2from1(1//3) atol=1e-12) == 1//3
     end
 
     @testset "acc" begin