
// Make newform 128.2.g.b in Magma, downloaded from the LMFDB on 25 April 2024.
// To make the character of type GrpDrchElt, type "MakeCharacter_128_g();"
// To make the character of type GrpDrchElt with Codomain the HeckeField, type "MakeCharacter_128_g_Hecke();"
// To make the coeffs of the qexp of the newform in the Hecke field type "qexpCoeffs();"
// To make the newform (type ModFrm), type "MakeNewformModFrm_128_2_g_b();".
// This may take a long time!  To see verbose output, uncomment the SetVerbose lines below.
// The precision argument determines an initial guess on how many Fourier coefficients to use.
// This guess is increased enough to uniquely determine the newform.
// To make the Hecke irreducible modular symbols subspace (type ModSym)
// containing the newform, type "MakeNewformModSym_128_2_g_b();".
// This may take a long time!  To see verbose output, uncomment the SetVerbose line below.
// The default sign is -1.  You can change this with the optional parameter "sign".
function ConvertToHeckeField(input: pass_field := false, Kf := [])
    if not pass_field then
        poly := [2, -12, 30, -44, 43, -28, 14, -4, 1];
        Kf := NumberField(Polynomial([elt : elt in poly]));
        AssignNames(~Kf, ["nu"]);
    end if;
    Rf_num := [[1, 0, 0, 0, 0, 0, 0, 0], [-5, 24, -37, 41, -27, 14, -4, 1], [-10, 30, -44, 43, -28, 14, -4, 1], [15, -66, 121, -146, 102, -59, 17, -5], [-19, 77, -133, 155, -105, 60, -17, 5], [20, -82, 145, -163, 113, -62, 18, -5], [23, -89, 152, -170, 115, -63, 18, -5], [31, -126, 223, -256, 175, -98, 28, -8]];
    Rf_basisdens := [1, 1, 1, 1, 1, 1, 1, 1];
    Rf_basisnums := ChangeUniverse([[z : z in elt] : elt in Rf_num], Kf);
    Rfbasis := [Rf_basisnums[i]/Rf_basisdens[i] : i in [1..Degree(Kf)]];
    inp_vec := Vector(Rfbasis)*ChangeRing(Transpose(Matrix([[elt : elt in row] : row in input])),Kf);
    return Eltseq(inp_vec);
end function;


// To make the character of type GrpDrchElt, type "MakeCharacter_128_g();"
function MakeCharacter_128_g()
    N := 128;
    order := 8;
    char_gens := [127, 5];
    v := [8, 7];
    // chi(gens[i]) = zeta^v[i]
    assert UnitGenerators(DirichletGroup(N)) eq char_gens;
    F := CyclotomicField(order);
    chi := DirichletCharacterFromValuesOnUnitGenerators(DirichletGroup(N,F),[F|F.1^e:e in v]);
    return MinimalBaseRingCharacter(chi);
end function;

// To make the character of type GrpDrchElt with Codomain the HeckeField, type "MakeCharacter_128_g_Hecke();"
function MakeCharacter_128_g_Hecke(Kf)
    N := 128;
    order := 8;
    char_gens := [127, 5];
    char_values := [[1, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, -1, 0, 0, 0]];
    assert UnitGenerators(DirichletGroup(N)) eq char_gens;
    values := ConvertToHeckeField(char_values : pass_field := true, Kf := Kf); // the value of chi on the gens as elements in the Hecke field
    F := Universe(values);// the Hecke field
    chi := DirichletCharacterFromValuesOnUnitGenerators(DirichletGroup(N,F),values);
    return chi;
end function;


function ExtendMultiplicatively(weight, aps, character)
    prec := NextPrime(NthPrime(#aps)) - 1; // we will able to figure out a_0 ... a_prec
    primes := PrimesUpTo(prec);
    prime_powers := primes;
    assert #primes eq #aps;
    log_prec := Floor(Log(prec)/Log(2)); // prec < 2^(log_prec+1)
    F := Universe(aps);
    FXY<X, Y> := PolynomialRing(F, 2);
    // 1/(1 - a_p T + p^(weight - 1) * char(p) T^2) = 1 + a_p T + a_{p^2} T^2 + ...
    R<T> := PowerSeriesRing(FXY : Precision := log_prec + 1);
    recursion := Coefficients(1/(1 - X*T + Y*T^2));
    coeffs := [F!0: i in [1..(prec+1)]];
    coeffs[1] := 1; //a_1
    for i := 1 to #primes do
        p := primes[i];
        coeffs[p] := aps[i];
        b := p^(weight - 1) * F!character(p);
        r := 2;
        p_power := p * p;
        //deals with powers of p
        while p_power le prec do
            Append(~prime_powers, p_power);
            coeffs[p_power] := Evaluate(recursion[r + 1], [aps[i], b]);
            p_power *:= p;
            r +:= 1;
        end while;    
    end for;
    Sort(~prime_powers);
    for pp in prime_powers do
        for k := 1 to Floor(prec/pp) do
            if GCD(k, pp) eq 1 then
                coeffs[pp*k] := coeffs[pp]*coeffs[k];
            end if;
        end for;
    end for;
    return coeffs;
end function;


function qexpCoeffs()
    // To make the coeffs of the qexp of the newform in the Hecke field type "qexpCoeffs();"
    weight := 2;
    raw_aps := [[0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 1, 0, 0, 0, 1, -1], [0, 0, 0, 0, 0, 0, -1, -1], [1, 0, -1, 0, 1, -1, -1, -1], [-1, 1, 0, 0, 0, 0, -1, 1], [-2, 0, 0, -2, 1, 0, 0, -1], [2, -1, -1, 1, -3, 1, 1, 2], [0, -1, 0, -1, -1, 1, 0, 1], [1, -1, 0, -1, 0, 0, -2, 1], [0, 2, 0, 0, -1, 2, 2, -1], [-4, 0, 0, 0, 2, 0, 2, 0], [0, 0, -2, 2, 0, -2, 1, 3], [1, -2, 0, -2, 0, 0, -4, 1], [1, 1, 0, 0, 2, 0, 3, -3], [0, 1, 1, 1, 1, 1, 1, 2], [0, 2, 2, 2, 2, 0, 5, -3], [3, 0, -1, 1, -3, -1, -4, -3], [2, -2, 2, 0, 1, -2, 2, -1], [6, 0, -3, 0, 0, 0, 3, 3], [3, 0, 3, 0, 5, 3, 3, -3], [-3, 1, -1, 1, -1, 1, 1, -3], [-4, 1, 1, -3, -1, -3, 3, -6], [-4, 3, 0, 3, -3, -3, 4, 3], [-1, -1, -3, 1, -5, -3, -3, 3], [4, 1, -1, 1, 3, -1, 3, 0], [-4, 0, 2, -2, 4, 2, -3, -5], [-1, -4, -1, 4, -3, -1, -1, 9], [-5, -3, 0, 0, -8, 0, 3, -3], [4, -4, 0, 0, -5, 4, 0, 5], [-2, 2, 2, 0, 0, 0, 4, 4], [4, 4, -4, 0, -2, 0, -2, 0], [0, 0, 1, 0, 6, 0, 1, 5], [7, -2, -2, -2, -2, 2, 2, 7], [3, 1, 4, 4, 4, 0, 1, 3], [0, 0, -2, -2, 0, 0, -3, 1], [-3, -1, 0, -1, 0, 0, -14, -3], [-2, -2, 2, 0, -7, -2, -2, -9], [-6, 0, -3, 0, -6, 0, -9, -3], [-3, 4, 3, -4, -3, 3, 3, -5], [2, 2, 0, -2, 7, -2, -6, -7], [-2, 3, 0, -1, 11, -3, -2, -11], [4, 0, 0, 0, 4, 0, -7, 7], [8, -4, 4, 0, -2, 0, -2, 0], [4, 3, -3, -1, -7, 1, -7, 0], [4, 0, -2, 2, -4, -4, -5, -3], [9, -4, -1, 4, -7, -1, -1, -1], [8, -5, 0, -1, -7, 5, -4, 7], [-8, 0, 0, -8, -2, 8, -2, 0], [0, -4, 1, 0, -4, -4, -3, -5], [8, 0, -4, 4, -8, 0, -5, -1], [-11, -1, 5, -1, 5, -5, 3, -11], [0, 1, 1, 1, 3, 1, -1, 18], [6, -7, -7, -1, -1, -1, -13, 6], [5, 0, -5, 5, -5, -1, -2, 3], [0, 2, -2, -8, 0, 8, 0, 0], [-9, 4, -5, -4, 13, -5, -5, 1], [-8, -2, 0, 4, 1, 2, 14, -1], [4, 1, 1, 5, -11, 5, 13, 6], [-12, 6, 4, 4, -6, 0, -3, 7], [-3, 3, 3, -3, 1, 3, 3, -3], [-9, 0, -1, 1, 9, -1, 2, 3], [8, 0, 2, -2, -8, 8, 11, 9], [6, -5, 0, -1, -7, 5, -2, 7], [-5, -1, 4, -1, 4, -4, 6, -5], [5, -6, 0, 6, 0, 0, 0, 7], [8, 0, -8, 0, -7, 0, 0, 1], [-7, 5, 4, 4, -2, 0, 5, -1], [-4, 2, 2, -2, 2, -2, 2, 0], [5, 0, 3, -3, -5, 3, 14, 11], [-8, 4, 12, 0, 9, 4, 8, -3], [-4, 2, -2, 8, 0, -8, 0, 0], [3, -4, -5, 4, -15, -5, -5, 5], [0, -3, -3, -3, 9, -3, -15, -10], [-8, 2, 0, 0, -6, 0, 5, -5], [-3, 0, 3, -3, 3, -5, -6, -9], [8, 8, -8, 4, 0, -4, 0, 0], [-16, 0, 6, -6, 16, -6, 5, -1], [-4, 2, 0, 4, 13, -2, 6, -13], [-6, 7, 7, 1, 9, 1, 5, -6], [1, 0, -2, 0, -6, -2, -2, -1], [4, 12, 5, 0, 2, 12, 21, -3], [4, 0, 2, -2, -4, 8, 11, 9], [0, -3, -3, -3, -9, -3, 3, -2], [-2, -1, -1, -3, 5, -3, -7, 10], [-1, -5, -4, -5, -4, 4, -6, -1], [-7, 0, 7, -7, 7, 11, 0, -7], [-4, -5, 5, -1, -3, 1, -3, 0], [5, -4, -6, -4, -6, 6, 2, 5], [8, 0, 0, 4, -17, 0, -4, 17], [0, -3, -3, -3, -5, -3, -1, 14], [0, -5, 0, 3, -1, 5, 8, 1], [-4, -4, 4, 0, -10, 0, -10, 0], [-7, 0, 3, 0, 17, 3, 3, 7], [5, -3, -8, -8, 2, 0, -13, 5], [-18, 7, 0, -5, 11, -7, 6, -11], [-19, 3, 4, 3, 4, -4, 2, -19], [-10, -4, 6, 0, 19, -4, -8, 13], [-13, 0, -4, 0, -4, 4, -4, -13], [-5, -3, -12, -12, -8, 0, -9, -3], [10, -2, -10, 0, -15, -2, -2, -5], [6, -4, -3, 0, 8, -4, -1, 11], [18, -6, 0, 2, -5, 6, -10, 5], [20, -5, 0, 7, -13, 5, -8, 13], [-13, 8, 4, -8, 4, 4, 4, -3], [1, 0, -1, 1, -1, 3, 8, 9], [-2, -6, 6, -2, 6, 2, 6, 0], [13, 1, 4, 4, 14, 0, 17, -13], [-4, 6, 6, 2, 6, 2, 6, -12], [15, -5, -4, -5, -4, 4, -18, 15], [11, -1, -11, 1, 11, -11, -11, -9], [12, 4, -4, 4, 0, -4, 0, 0], [-16, 0, -2, 2, 16, -4, -13, -11], [7, -1, 3, -1, 3, -3, -19, 7], [11, 1, 8, 8, 12, 0, 7, 1], [1, -1, 4, -1, 4, -4, 6, 1], [8, 1, -1, 5, -13, -5, -13, 0], [-6, -8, 5, 0, 4, -8, -9, -1], [-9, 0, -5, 0, -7, -5, -5, 9], [-12, 2, 0, -12, 17, -2, -2, -17], [-4, -5, 0, -13, 9, 5, -4, -9], [4, -8, 0, 0, -4, 0, -15, 15], [-8, 11, -11, 3, 13, -3, 13, 0], [4, 0, -10, 10, -4, -6, 9, 19], [-17, 13, 8, 8, -4, 0, 9, -1], [-20, 3, 0, 7, -7, -3, 24, 7], [10, -4, 2, 0, -5, -4, 8, -7], [0, 0, 8, -8, 0, -10, -15, -23], [0, 5, 5, 5, 15, 5, -5, -2], [3, -13, -4, -13, -4, 4, -6, 3], [4, 4, -4, 0, 17, 4, 4, 21], [2, -4, 9, 0, 14, -4, 7, 5], [25, 0, -1, 0, 9, -1, -1, -25], [12, -3, -3, 9, -17, 9, 11, -10], [0, -12, -2, -2, -12, 0, 5, -7], [5, -12, 2, 12, -10, 2, 2, 19], [8, -7, 7, -3, 11, 3, 11, 0], [-20, 0, 0, 0, 20, 6, -3, -3], [-2, 3, 0, -1, 7, -3, -2, -7], [-14, 4, 14, 0, -1, 4, 4, -15], [-3, 4, -2, 4, -2, 2, 14, -3], [1, 1, -8, -8, 2, 0, -19, 11], [12, 10, 8, 8, 22, 0, 17, -9], [-1, 3, -4, 3, -4, 4, -10, -1], [-21, 0, 3, -3, 21, -1, -10, -13], [10, 0, -10, 0, 3, 0, 0, 13], [-15, 0, -5, 0, 9, -5, -5, 15], [-4, -6, 6, 6, -10, 0, 9, -3], [-5, 6, 2, -6, 14, 2, 2, -7], [13, 0, -1, 1, -13, -5, -26, -25], [0, -4, 4, 0, -10, 0, -10, 0], [4, 0, 0, 4, -13, 0, 0, 13], [0, -8, -8, -8, -8, -8, -8, -4], [4, -5, 0, 3, -5, 5, 4, 5], [-13, -13, 8, -13, 8, -8, -2, -13], [3, -3, 8, 8, 0, 0, 21, -13], [-12, 9, 9, -3, 13, -3, 5, -22], [1, 15, 0, 15, 0, 0, 34, 1], [8, -9, 9, -9, 13, 9, 13, 0], [1, -9, 1, -9, 1, -1, -25, 1], [8, 8, 0, 4, 11, -8, -12, -11], [2, 11, 0, -9, 9, -11, -22, -9], [7, -8, 4, 8, -20, 4, 4, 9], [-7, 4, 7, -4, -23, 7, 7, -1], [17, -3, -8, -8, 14, 0, 7, -15], [-10, 1, 1, -9, -5, -9, 7, -10], [23, 3, 0, 3, 0, 0, -14, 23], [12, -8, 8, 12, -4, -12, -4, 0], [0, 0, 12, -12, 0, 10, 13, 1]];
    aps := ConvertToHeckeField(raw_aps);
    chi := MakeCharacter_128_g_Hecke(Universe(aps));
    return ExtendMultiplicatively(weight, aps, chi);
end function;


// To make the newform (type ModFrm), type "MakeNewformModFrm_128_2_g_b();".
// This may take a long time!  To see verbose output, uncomment the SetVerbose lines below.
// The precision argument determines an initial guess on how many Fourier coefficients to use.
// This guess is increased enough to uniquely determine the newform.
function MakeNewformModFrm_128_2_g_b(:prec:=8)
    chi := MakeCharacter_128_g();
    f_vec := qexpCoeffs();
    Kf := Universe(f_vec);
    // SetVerbose("ModularForms", true);
    // SetVerbose("ModularSymbols", true);
    S := CuspidalSubspace(ModularForms(chi, 2));
    S := BaseChange(S, Kf);
    maxprec := NextPrime(997) - 1;
    while true do
        trunc_vec := Vector(Kf, [0] cat [f_vec[i]: i in [1..prec]]);
        B := Basis(S, prec + 1);
        S_basismat := Matrix([AbsEltseq(g): g in B]);
        if Rank(S_basismat) eq Min(NumberOfRows(S_basismat), NumberOfColumns(S_basismat)) then
            S_basismat := ChangeRing(S_basismat,Kf);
            f_lincom := Solution(S_basismat,trunc_vec);
            f := &+[f_lincom[i]*Basis(S)[i] : i in [1..#Basis(S)]];
            return f;
        end if;
        error if prec eq maxprec, "Unable to distinguish newform within newspace";
        prec := Min(Ceiling(1.25 * prec), maxprec);
    end while;
end function;


// To make the Hecke irreducible modular symbols subspace (type ModSym)
// containing the newform, type "MakeNewformModSym_128_2_g_b();".
// This may take a long time!  To see verbose output, uncomment the SetVerbose line below.
// The default sign is -1.  You can change this with the optional parameter "sign".
function MakeNewformModSym_128_2_g_b( : sign := -1)
    R<x> := PolynomialRing(Rationals());
    chi := MakeCharacter_128_g();
    // SetVerbose("ModularSymbols", true);
    Snew := NewSubspace(CuspidalSubspace(ModularSymbols(chi,2,sign)));
    Vf := Kernel([<3,R![4, 16, 96, 24, -32, 0, 8, -4, 1]>],Snew);
    return Vf;
end function;