From b01b6689d7a2008999654d4d7b0fd11365122c36 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Beno=C3=AEt=20Legat?= <benoit.legat@gmail.com>
Date: Thu, 22 Jun 2023 18:02:58 +0200
Subject: [PATCH] Fixes for SIMDPolynomials (#267)

* Fixes for SIMDPolynomials

* Fix format
---
 src/monomial.jl      |  3 ++-
 src/show.jl          |  6 ++---
 src/substitution.jl  | 54 ++++++++++++++++++++++++++++++++++++++------
 test/substitution.jl | 10 ++++++++
 4 files changed, 62 insertions(+), 11 deletions(-)

diff --git a/src/monomial.jl b/src/monomial.jl
index 783a9bae..db40488e 100644
--- a/src/monomial.jl
+++ b/src/monomial.jl
@@ -101,7 +101,8 @@ end
 
 Returns whether the monomial of `t` is constant.
 """
-isconstant(t::AbstractTermLike) = all(iszero, exponents(t))
+isconstant(t::AbstractTerm) = isconstant(monomial(t))
+isconstant(t::AbstractMonomialLike) = all(iszero, exponents(t))
 isconstant(v::AbstractVariable) = false
 
 """
diff --git a/src/show.jl b/src/show.jl
index 7f573e14..92df2050 100644
--- a/src/show.jl
+++ b/src/show.jl
@@ -34,10 +34,10 @@ function _show(io::IO, mime::MIME, var::AbstractVariable)
         print_subscript(io, mime, indices)
     end
 end
-function _show(io::IO, mime::MIME"text/print", var::AbstractVariable)
-    return print(io, name(var))
-end
 
+function print_subscript(io::IO, ::MIME"text/print", index)
+    return print(io, "[", join(index, ","), "]")
+end
 function print_subscript(io::IO, ::MIME"text/latex", index)
     return print(io, "_{", join(index, ","), "}")
 end
diff --git a/src/substitution.jl b/src/substitution.jl
index c05766c9..f370bfe1 100644
--- a/src/substitution.jl
+++ b/src/substitution.jl
@@ -81,8 +81,39 @@ function powersubstitute(
 )
     return powersubstitute(st, s, p) * powersubstitute(st, s, p2...)
 end
+
+function _promote_subs(S, T, s::Substitution)
+    # `T` is a constant
+    return T
+end
+
+function _promote_subs(S, T::Type{<:Union{RationalPoly,_APL}}, s::Substitution)
+    return MA.promote_operation(substitute, S, T, typeof(s))
+end
+
+function _promote_subs(S, T, s::AbstractMultiSubstitution)
+    return _promote_subs(
+        S,
+        T,
+        pair_zip(_monomial_vector_to_variable_tuple(s))...,
+    )
+end
+
+function _promote_subs(
+    S,
+    T,
+    head::AbstractSubstitution,
+    tail::Vararg{AbstractSubstitution,N},
+) where {N}
+    return _promote_subs(S, _promote_subs(S, T, head), tail...)
+end
+
 function substitute(st::_AST, m::AbstractMonomial, s::Substitutions)
-    return powersubstitute(st, s, powers(m)...)
+    if isconstant(m)
+        return one(_promote_subs(typeof(st), typeof(m), s...))
+    else
+        return powersubstitute(st, s, powers(m)...)
+    end
 end
 
 ## Terms
@@ -92,11 +123,20 @@ end
 
 function MA.promote_operation(
     ::typeof(substitute),
-    ::Type{Subs},
+    ::Type{Eval},
+    ::Type{M},
+    ::Type{Pair{V,T}},
+) where {M<:AbstractMonomial,V<:AbstractVariable,T}
+    return MA.promote_operation(*, T, T)
+end
+
+function MA.promote_operation(
+    ::typeof(substitute),
+    ::Type{S},
     ::Type{T},
     args::Vararg{Type,N},
-) where {T<:AbstractTerm,N}
-    M = MA.promote_operation(substitute, Subs, monomial_type(T), args...)
+) where {S<:AbstractSubstitutionType,T<:AbstractTerm,N}
+    M = MA.promote_operation(substitute, S, monomial_type(T), args...)
     U = coefficient_type(T)
     return MA.promote_operation(*, U, M)
 end
@@ -121,11 +161,11 @@ end
 
 function MA.promote_operation(
     ::typeof(substitute),
-    ::Type{Subs},
+    ::Type{S},
     ::Type{P},
     args::Vararg{Type,N},
-) where {P<:AbstractPolynomial,N}
-    T = MA.promote_operation(substitute, Subs, term_type(P), args...)
+) where {S<:AbstractSubstitutionType,P<:AbstractPolynomial,N}
+    T = MA.promote_operation(substitute, S, term_type(P), args...)
     return MA.promote_operation(+, T, T)
 end
 
diff --git a/test/substitution.jl b/test/substitution.jl
index 76488ef1..3e0deb1e 100644
--- a/test/substitution.jl
+++ b/test/substitution.jl
@@ -1,5 +1,8 @@
+using Test
 import Test: @inferred
 
+import MutableArithmetics as MA
+
 @testset "Substitution" begin
     Mod.@polyvar x[1:3]
 
@@ -28,6 +31,8 @@ import Test: @inferred
     p = x[1] + x[2] + 2 * x[1]^2 + 3 * x[1] * x[2]^2
     #@inferred p((x[1], x[2]) => (1.0, 2.0))
 
+    m = x[1] * x[2]
+    @inferred subs(m, x[2] => 2.0)
     @inferred subs(p, x[2] => 2.0)
     @test subs(p, x[2] => 2.0) == 13x[1] + 2 + 2x[1]^2
     @inferred subs(p, x[2] => x[1])
@@ -77,4 +82,9 @@ import Test: @inferred
         @test t == @inferred subs(t, x => 1.0x)
         @test t == @inferred subs(t, x => 1.0)
     end
+
+    for (p, s) in [(x^1, x => 2x)]
+        @test MA.promote_operation(substitute, Subs, typeof(p), typeof(s)) ==
+              typeof(subs(p, s))
+    end
 end