reverted solve_for merge

src/linear_algebra.jl

@@ -105,9 +105,7 @@ function solve_for(eq, var; simplify=false, check=true) # scalar case
     else
         x = a \ -b
     end
-    x = length(var) == 1 ? x :  Dict(v => ans for (v, ans) in zip(var, x))
-    simplify || return [x]
-
+    simplify || return x
     if x isa AbstractArray
         SymbolicUtils.simplify.(simplify_fractions.(x))
     else

src/solver/main.jl

@@ -134,22 +134,17 @@ function solve(expr, x, multiplicities=false)
         expr = Vector{Num}(expr)
     end
 
-    # the islinear outputted here is breaks a lot:
-    # a, b, islinear = linear_expansion(expr, x)
-    # islinear && return map(postprocess_root, solve_for(expr, x))
 
     if x_univar
+
         sols = []
         if expr_univar
-            sols = !check_poly_inunivar(expr, x) ? ia_solve(expr, x) :
-                islinear(expr, [x]) ? solve_for(expr, x) :
-                   solve_univar(expr, x, multiplicities)
+            sols = check_poly_inunivar(expr, x) ? solve_univar(expr, x, multiplicities) : ia_solve(expr, x)
         else
             for i in eachindex(expr)
                 !check_poly_inunivar(expr[i], x) && throw("Solve can not solve this input currently")
             end
-            sols = all(e->islinear(e, [x]), expr) ? solve_for(expr, x) : 
-                    solve_multipoly(expr, x, multiplicities)
+            sols = solve_multipoly(expr, x, multiplicities)
         end
 
         sols = map(postprocess_root, sols)
@@ -162,8 +157,8 @@ function solve(expr, x, multiplicities=false)
                 @assert check_poly_inunivar(e, var) "This system can not be currently solved by solve."
             end
         end
-        
-        sols = all(e->islinear(e, x), expr) ? solve_for(expr, x) : solve_multivar(expr, x, multiplicities)
+
+        sols = solve_multivar(expr, x, multiplicities)
         for sol in sols
             for var in x
                 sol[var] = postprocess_root(sol[var])

src/solver/solve_helpers.jl

@@ -98,23 +98,6 @@ function check_poly_inunivar(poly, var)
     return isequal(constant, 0)
 end
 
-function islinear(expr, vars)
-    for var in vars
-        subs, filtered_expr = filter_poly(expr, var)
-        coeffs, constant = polynomial_coeffs(filtered_expr, [var])
-
-        !isequal(constant, 0) && return false
-        sdegree(coeffs, var) > 1 && return false
-        delete!(coeffs, 1)
-
-        vals = collect(values(coeffs))
-        for val in vals
-            any(x->n_occurrences(val, x) > 0, vars) && return false
-        end
-    end
-    return true
-end
-
 function f_numbers(n)
     n = unwrap(n)
     if n isa ComplexTerm || n isa Float64 || n isa Irrational