
// Make newform 784.4.f.e in Magma, downloaded from the LMFDB on 25 April 2024.
// To make the character of type GrpDrchElt, type "MakeCharacter_784_f();"
// To make the character of type GrpDrchElt with Codomain the HeckeField, type "MakeCharacter_784_f_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_784_4_f_e();".
// 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_784_4_f_e();".
// 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, 0, 4, 0, 1];
        Kf := NumberField(Polynomial([elt : elt in poly]));
        AssignNames(~Kf, ["nu"]);
    end if;
    Rf_num := [[1, 0, 0, 0], [0, 0, 0, 1], [0, 7, 0, 2], [14, 0, 7, 0]];
    Rf_basisdens := [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_784_f();"
function MakeCharacter_784_f()
    N := 784;
    order := 2;
    char_gens := [687, 197, 689];
    v := [1, 2, 1];
    // 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_784_f_Hecke();"
function MakeCharacter_784_f_Hecke(Kf)
    N := 784;
    order := 2;
    char_gens := [687, 197, 689];
    char_values := [[-1, 0, 0, 0], [1, 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 := 4;
    raw_aps := [[0, 0, 0, 0], [0, 0, 0, 0], [0, -1, -5, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 4, 21, 0], [0, 6, -29, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, -11], [0, 0, 0, 0], [0, 0, 0, -13], [0, -51, 83, 0], [0, 0, 0, 0], [0, 0, 0, 0], [572, 0, 0, 0], [0, 0, 0, 0], [0, -152, -41, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 163, 193, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, -226, 157, 0], [0, -217, 257, 0], [0, 224, 373, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, -229], [1328, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, -313], [0, 0, 0, 0], [-940, 0, 0, 0], [0, 0, 0, 0], [0, 581, -219, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, -579, -731, 0], [0, 0, 0, 0], [0, 127, -1049, 0], [0, 0, 0, 0], [-72, 0, 0, 0], [-1174, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 73, 1561, 0], [0, 0, 0, -549], [0, 0, 0, 0], [0, -382, 1509, 0], [0, 0, 0, 0], [0, 1047, -907, 0], [0, 0, 0, 0], [0, -1068, -1501, 0], [0, 0, 0, 0], [-9126, 0, 0, 0], [0, 0, 0, -117], [0, 0, 0, 0], [0, 1592, 67, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 1733, 843, 0], [-10274, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 913], [0, 0, 0, 0], [0, 1957, 1389, 0], [0, -2071, 211, 0], [0, 0, 0, 0], [0, 0, 0, 0], [-6372, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 1069], [0, 476, -3379, 0], [0, 0, 0, -963], [0, -1621, 2597, 0], [0, 0, 0, 0], [-10890, 0, 0, 0], [0, 0, 0, 0], [0, -1934, -3371, 0], [0, 0, 0, 0], [0, 0, 0, 0], [10120, 0, 0, 0], [10456, 0, 0, 0], [0, 2643, -1901, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, -3324, -2837, 0], [0, -1907, -4981, 0], [0, 0, 0, 0], [-24460, 0, 0, 0], [0, 0, 0, 0], [8626, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, -1609], [0, 0, 0, 0], [0, 2458, 5647, 0], [0, 0, 0, 0], [0, -474, 6329, 0], [0, 0, 0, 0], [0, -2219, 5367, 0], [0, 0, 0, 0], [0, 0, 0, -3055], [0, 0, 0, -2995], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, -3123], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, -2455], [0, 0, 0, 0], [0, 4999, 3963, 0], [0, 0, 0, 2155], [0, -5289, 1631, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, -3663], [0, 0, 0, 2029], [0, 0, 0, 0], [0, 0, 0, 0], [0, -4013, -7673, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 895], [0, -6506, -3577, 0], [0, -4346, -8213, 0], [0, 417, 9677, 0], [0, 0, 0, 0], [0, 7156, 491, 0], [23270, 0, 0, 0], [0, 0, 0, 0], [1850, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 328, -10599, 0], [0, 0, 0, 0], [0, -7951, -1119, 0], [0, -5138, 7583, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, -905], [0, 4722, 10591, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 1018, -12379, 0], [0, 7187, 9393, 0], [0, -7944, -8143, 0], [0, 0, 0, 0], [56758, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 2405], [0, 0, 0, 0], [0, 0, 0, 0], [0, 1103, -13773, 0]];
    aps := ConvertToHeckeField(raw_aps);
    chi := MakeCharacter_784_f_Hecke(Universe(aps));
    return ExtendMultiplicatively(weight, aps, chi);
end function;


// To make the newform (type ModFrm), type "MakeNewformModFrm_784_4_f_e();".
// 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_784_4_f_e(:prec:=4)
    chi := MakeCharacter_784_f();
    f_vec := qexpCoeffs();
    Kf := Universe(f_vec);
    // SetVerbose("ModularForms", true);
    // SetVerbose("ModularSymbols", true);
    S := CuspidalSubspace(ModularForms(chi, 4));
    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_784_4_f_e();".
// 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_784_4_f_e( : sign := -1)
    R<x> := PolynomialRing(Rationals());
    chi := MakeCharacter_784_f();
    // SetVerbose("ModularSymbols", true);
    Snew := NewSubspace(CuspidalSubspace(ModularSymbols(chi,4,sign)));
    Vf := Kernel([<3,R![0, 1]>],Snew);
    return Vf;
end function;