Add map_or

Author: jakobnissen

NEWS.md

@@ -1,3 +1,8 @@
+## Release 0.5.1
+
+__New features__
+* New function `map_or(f, x::Result, v)`. Returns `f(unwrap(x))` if x is a result value, else `v`
+
 ## Release 0.5.0
 
 __Breaking changes__

Project.toml

@@ -1,7 +1,7 @@
 name = "ErrorTypes"
 uuid = "7f495686-c6d2-4c77-9e8e-e4c865675f9d"
 authors = ["Jakob Nybo Nissen <[email protected]>"]
-version = "0.5.0"
+version = "0.5.1"
 
 [compat]
 julia = "1.3"

src/ErrorTypes.jl

@@ -224,6 +224,13 @@ function and_then(f, ::Type{T}, x::Result{O, E})::Result{T, E} where {T, O, E}
     Result{T, E}(data isa Ok ? Ok(f(data.x)) : Err(data.x))
 end
 
+"""
+    map_or(f, x::Result, v)
+
+If `x` is a result value, return `f(unwrap(x))`. Else, return `v`.
+"""
+map_or(f, x::Result{O, E}, v) where {O, E} = f(@unwrap_or x return v)
+
 """
     unwrap_or(x::Result, v)
 
@@ -266,7 +273,7 @@ base(x::Option{T}) where T = Some(@unwrap_or x (return nothing))
 export Ok, Err, Result, Option,
     is_error, some, none,
     unwrap, unwrap_error, expect, expect_error,
-    and_then, unwrap_or, unwrap_error_or, flatten, base,
+    and_then, unwrap_or, map_or, unwrap_error_or, flatten, base,
     @?, @unwrap_or, @unwrap_error_or
 
 end

test/runtests.jl

@@ -82,6 +82,12 @@ using Test
     @test and_then(x -> abs(x) % UInt8, UInt8, Result{Int, Dict}(Ok(-55))) === Result{UInt8, Dict}(Ok(UInt8(55)))
     @test and_then(x -> x + 1, Bool, Result{String, Int}(Err(1))) === Result{Bool, Int}(Err(1))
     @test and_then(x -> "foo", Dict, Result{Int, Int}(Err(1))) === Result{Dict, Int}(Err(1))
+
+    # map_or
+    @test map_or(x -> x + 1, Result{Float64, String}(Ok(3.0)), 3.0) === 4.0
+    @test map_or(x -> x + 1, Result{Float64, String}(Err("foo")), 3.0) === 3.0
+    @test map_or(x -> 0, Result{Int, Int}(Ok(5)), 1) === 0
+    @test map_or(x -> 0, Result{Int, Int}(Err(19)), 1) === 1
 end
 
 @testset "Option" begin