avoid problem with valuation(a,p) if 1st argument is zero

Author: HaraldHofstaetter

src/parametric_problems.jl

@@ -60,8 +60,8 @@ function ParamRdeSpecialDenomExp(a::P, b::F, gs::Vector{F}, D::Derivation) where
     t = gen(parent(a))
     degree(gcd(t, a))==0 || error("gcd(a, t) must be == 1")
     p = t
-    nb = valuation(b, p)
-    nc = minimum([valuation(g, p) for g in gs])
+    nb = iszero(b) ? typemax(Int) : valuation(b, p)
+    nc = minimum([iszero(g) ? typemax(Int) : valuation(g, p) for g in gs])
     n = min(0, nc - min(0, nb))
     if nb==0 
         α = constant_coefficient(Remainder(-b//a, p))
@@ -109,8 +109,8 @@ function ParamRdeSpecialDenomTan(a::P, b::F, gs::Vector{F}, D::Derivation) where
     t = gen(parent(a))
     p = t^2+1
     degree(gcd(a, p))==0 || error("gcd(a, t^2+1) must be == 1")
-    nb = valuation(b, p)
-    nc = minimum([valuation(g, p) for g in gs])
+    nb = iszero(b) ? typemax(Int) : valuation(b, p)
+    nc = minimum([iszero(g) ? typemax(Int) : valuation(g, p) for g in gs])
     n = min(0, nc - min(0, nb))
     if nb==0         
         αI_plus_β = Remainder(-b//a, p)
@@ -997,7 +997,7 @@ function LimitedIntegrateReduce(f::F, ws::Vector{F}, D::Derivation) where
        hs = lcm(vcat(ds, [es for (en, es) in eness]))
        h = hn*hs # in Bronsteins's book, wrongly a = hn*hs
        b = -D(hn)-divexact(hn*D(hs),hs)
-       μ = min(valuation_infinity(f), minimum([valuation_infinity(w) for w in ws]))
+       μ = min(iszero(f) ? typemax(Int) : valuation_infinity(f), minimum([iszero(w) ? typemax(Int) : valuation_infinity(w) for w in ws]))
        N = degree(hn) + degree(hs) + max(0, 1 - degree(D) - μ)
     end
     hhn = h*hn 

src/risch_diffeq.jl

@@ -218,8 +218,8 @@ function RdeSpecialDenomExp(a::P, b::F, c::F, D::Derivation) where
     t = gen(parent(a))
     degree(gcd(t, a))==0 || error("gcd(a, t) must be == 1")
     p = t
-    nb = valuation(b, p)
-    nc = valuation(c, p)
+    nb = iszero(b) ? typemax(Int) : valuation(b, p)
+    nc = iszero(c) ? typemax(Int) : valuation(c, p)
     n = min(0, nc - min(0, nb))
     if nb==0 
         α = constant_coefficient(Remainder(-b//a, p))
@@ -264,8 +264,8 @@ function RdeSpecialDenomTan(a::P, b::F, c::F, D::Derivation) where
     t = gen(parent(a))
     p = t^2+1
     degree(gcd(a, p))==0 || error("gcd(a, t^2+1) must be == 1")
-    nb = valuation(b, p)
-    nc = valuation(c, p)
+    nb = iszero(b) ? typemax(Int) : valuation(b, p)
+    nc = iszero(c) ? typemax(Int) : valuation(c, p)
     n = min(0, nc - min(0, nb))
     if nb==0         
         αI_plus_β = Remainder(-b//a, p)
@@ -322,8 +322,8 @@ function RdeSpecialDenomTanI(a::P, b::F, c::F, D::Derivation) where
     contains_I(parent(a)) || error("field k must contain I=sqrt(-1)")
     I = get_I(base_ring(parent(a)))
     p = t-I
-    nb = valuation(b, p)
-    nc = valuation(c, p)
+    nb = iszero(b) ? typemax(Int) : valuation(b, p) 
+    nc = iszero(c) ? typemax(Int) : valuation(c, p)
     n = min(0, nc - min(0, nb))
     if nb==0         
         α = constant_coefficient(Remainder(-b//a, p))

src/transcendental_functions.jl

@@ -329,7 +329,7 @@ function IntegrateHypertangentReduced(p::F, D::Derivation) where
     end
     t = gen(base_ring(parent(p)))    
     Q = t^2+1
-    m = -valuation(p, Q)
+    m = -(iszero(p) ? typemax(Int) : valuation(p, Q))
     if m<=0
         return Z, 1
     end