Added at-consts macro (#133)

Fixes #111

Also removed references to Julia 0.6 and 0.7 in the Readme & docs.

Author: mauro3

NEWS.md

@@ -1,3 +1,6 @@
+# 2021-01-22
+Added `@consts` macro to define a block of constants.
+
 # 2019-09-10
 Added support of packing immutables (by creating one) through `@pack_SomeType`.
 

README.md

@@ -61,8 +61,6 @@ julia> MyNT(x = 2)
 (x = 2, y = "foo", z = :bar)
 ```
 
-> v0.6 users: since `NamedTuples` are not supported in base Julia v0.6, you must import the `NamedTuples.jl` package. Be aware of [this issue](https://github.com/JuliaLang/julia/issues/17240) with keyword arguments in v0.6.
-
 Unpacking is done with `@unpack` (`@pack!` is similar):
 ```julia
 struct B
@@ -77,6 +75,16 @@ a = BB.a
 c = BB.c
 ```
 
+Defining several constants
+```julia
+@consts begin
+    a = 1
+    b = 2.0
+    c = "a"
+end
+```
+
+
 The features are:
 
 - a keyword constructor for the type
@@ -88,7 +96,8 @@ The features are:
 - packing and unpacking macros for the type: `@unpack_*` where `*` is
   the type name.
 - generic packing and unpacking macros `@pack!`, `@unpack` (work with
-  any types).
+  any types, via [UnPack.jl](https://github.com/mauro3/UnPack.jl))
+- `@consts` macro to defined a bunch of constants
 
 The keyword-constructor and default-values functionality will probably
 make it into Julia

docs/src/manual.md

@@ -136,10 +136,6 @@ re-definition warnings, then use [`@with_kw_noshow`](@ref).
 
 As mentioned in the README, the `@with_kw` macro can be used to decorate a named tuple and produce a named tuple constructor with those defaults.
 
-> Users of Julia v0.6 should be aware of this [caveat](https://github.com/JuliaLang/julia/issues/17240) that prohibits assignments like `@with_kw (f = f, x = x)`. This is a consequence of different scoping rules for keyword arguments in [v0.6](https://docs.julialang.org/en/stable/manual/functions/#Evaluation-Scope-of-Default-Values-1) and [v0.7](https://docs.julialang.org/en/latest/manual/functions/#Evaluation-Scope-of-Default-Values-1).
-
-> Users of v0.6 will also need to explicitly import `NamedTuples.jl`, since this functionality is not present in that version of base Julia.
-
 These named tuples can be defined as such:
 
 ```julia
@@ -178,6 +174,19 @@ julia> z
 
 Since the macro operates on a single tuple expression (as opposed to a tuple of assignment expressions),writing `@with_kw(x = 1, y = :foo)` will return an error suggesting you write `@with_kw (x = 1, y = :foo)`.
 
+# Blocks of constants
+
+Several constants can be defined like so:
+```julia
+@consts begin
+    a = 1
+    b = 2
+    c = 3
+end
+```
+(if you do the math, you'll need more than three constants in the block to actually save typing.)
+
+
 # (Un)pack macros
 
 ## `@unpack` and `@pack` re-exported from UnPack.jl

src/Parameters.jl

@@ -45,7 +45,7 @@ import Base: @__doc__
 import OrderedCollections: OrderedDict
 using UnPack: @unpack, @pack!
 
-export @with_kw, @with_kw_noshow, type2dict, reconstruct, @unpack, @pack!, @pack
+export @with_kw, @with_kw_noshow, type2dict, reconstruct, @unpack, @pack!, @pack, @consts
 
 ## Parser helpers
 #################
@@ -657,4 +657,25 @@ macro with_kw_noshow(typedef)
     return esc(with_kw(typedef, __module__, false))
 end
 
+###########
+# @consts macro
+
+"""
+
+"""
+macro consts(block)
+    @assert block.head == :block
+    args = block.args
+    for i in eachindex(args)
+        a = args[i]
+        if a isa LineNumberNode
+            continue
+        elseif a.head == :(=)
+            args[i] = Expr(:const, args[i])
+        else
+            error("Could not parse block")
+        end
+    end
+    return esc(block)
+end
 end # module

test/runtests.jl

@@ -668,3 +668,17 @@ z2 = TestModule.test_function(TestModule.TestStruct(; y = 9.0))
     @test foo()() == (x = 1, y = 2)
     @test foo()(y=4) == (x = 1, y = 4)
 end
+
+####
+# @consts
+####
+@consts begin
+    a34 = 1
+    b34 = 2.0
+    d34 = sin(56)
+end
+@test a34 == 1
+@test b34 == 2.0
+@test_throws ErrorException global b34 = 1
+## this test is dependent on Julia version, leave it:
+# @test_warn "WARNING: redefinition of constant b34. This may fail, cause incorrect answers, or produce other errors." global b34 = 4.0