
// Make newform 8015.2.a.d in Magma, downloaded from the LMFDB on 18 April 2024.
// To make the character of type GrpDrchElt, type "MakeCharacter_8015_a();"
// To make the coeffs of the qexp of the newform in the Hecke field type "qexpCoeffs();"
// To make the newform (type ModFrm), type "MakeNewformModFrm_8015_2_a_d();".
// 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_8015_2_a_d();".
// 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
        Kf := Rationals();
    end if;
    return [Kf!elt[1] : elt in input];
end function;


// To make the character of type GrpDrchElt, type "MakeCharacter_8015_a();"
function MakeCharacter_8015_a()
    N := 8015;
    order := 1;
    char_gens := [3207, 4581, 4586];
    v := [1, 1, 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;

function MakeCharacter_8015_a_Hecke(Kf)
    return MakeCharacter_8015_a();
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 := [[1], [0], [1], [1], [-4], [2], [-6], [-4], [0], [-10], [8], [-2], [-6], [8], [8], [6], [12], [-2], [-4], [0], [14], [0], [16], [-6], [2], [-18], [4], [-12], [-2], [6], [8], [20], [-2], [20], [-10], [-24], [18], [4], [-4], [14], [12], [6], [0], [-14], [-22], [-16], [-28], [24], [-12], [1], [10], [24], [18], [-12], [14], [16], [-10], [0], [22], [-30], [-4], [-18], [24], [-24], [14], [-6], [4], [26], [-8], [14], [6], [24], [-28], [-10], [28], [20], [-26], [30], [-14], [-22], [-28], [22], [-24], [34], [-8], [24], [18], [34], [-2], [4], [0], [24], [-8], [-28], [-20], [36], [30], [18], [-28], [-2], [28], [22], [4], [-22], [-20], [14], [8], [-6], [-24], [26], [-12], [-22], [18], [-20], [40], [-30], [-16], [-24], [26], [-20], [22], [34], [-6], [-16], [12], [30], [-34], [8], [-40], [14], [4], [28], [-24], [38], [18], [34], [34], [-40], [-6], [18], [44], [6], [32], [52], [38], [24], [26], [22], [-36], [-52], [-46], [2], [56], [-8], [24], [40], [32], [10], [-58], [30], [-36], [34], [4], [-12], [34], [32], [40], [-2], [58], [-34], [-36], [-26], [-24], [-26], [0], [-6], [-60], [-26], [-20], [30], [-4], [-36], [10], [-30], [60], [-42], [-22], [-52], [-38], [-32], [-18], [-36], [-20], [30], [40], [-46], [18], [-34], [-42], [60], [-10], [-8], [26], [-30], [-4], [-42], [8], [40], [-6], [-20], [30], [54], [-36], [52], [-48], [42], [-32], [10], [48], [-26], [46], [-64], [-22], [-4], [48], [22], [-18], [0], [56], [-12], [-6], [-4], [40], [34], [-52], [-8], [-70], [-70], [12], [16], [40], [20], [68], [22], [-26], [-40], [-68], [60], [-36], [-12], [34], [-6], [-44], [-30], [-14], [12], [22], [-4], [-6], [-2], [68], [0], [-74], [-78], [18], [28], [6], [58], [44], [-42], [14], [-8], [62], [48], [-38], [76], [-8], [-2], [-46], [68], [52], [16], [12], [-50], [60], [48], [30], [22], [-64], [50], [-58], [64], [-54], [28], [18], [-26], [64], [26], [44], [84], [-14], [6], [-56], [40], [-52], [2], [-12], [30], [-32], [-78], [0], [46], [82], [36], [4], [-38], [4], [-24], [-50], [-30], [-52], [-46], [-2], [-52], [-58], [50], [-20], [4], [-12], [-22], [54], [6], [-16], [-12], [36], [-20], [62], [-62], [58], [-68], [86], [-2], [-58], [40], [78], [20], [38], [-32], [-72], [26], [76], [46], [-66], [-8], [-10], [-14], [24], [-44], [-42], [0], [70], [58], [80], [-92], [60], [58], [46], [-52], [-30], [52], [-28], [-16], [54], [-24], [18], [84], [24], [70], [-22], [22], [22], [-26], [72], [42], [12], [36], [40], [22], [-52], [-12], [34], [6], [84], [28], [-48], [6], [32], [90], [-36], [-18], [-34], [-6], [4], [54], [-50], [-40], [-10], [-30], [-96], [92], [-6], [-46], [-24], [28], [38], [102], [24], [80], [-78], [0], [94], [-34], [-40], [-60], [102], [54], [-104], [74], [12], [24]];
    aps := ConvertToHeckeField(raw_aps);
    chi := MakeCharacter_8015_a_Hecke(Universe(aps));
    return ExtendMultiplicatively(weight, aps, chi);
end function;


// To make the newform (type ModFrm), type "MakeNewformModFrm_8015_2_a_d();".
// 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_8015_2_a_d(:prec:=1)
    chi := MakeCharacter_8015_a();
    f_vec := qexpCoeffs();
    Kf := Universe(f_vec);
    // SetVerbose("ModularForms", true);
    // SetVerbose("ModularSymbols", true);
    S := CuspidalSubspace(ModularForms(chi, 2));
    S := BaseChange(S, Kf);
    maxprec := NextPrime(2999) - 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_8015_2_a_d();".
// 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_8015_2_a_d( : sign := -1)
    R<x> := PolynomialRing(Rationals());
    chi := MakeCharacter_8015_a();
    // SetVerbose("ModularSymbols", true);
    Snew := NewSubspace(CuspidalSubspace(ModularSymbols(chi,2,sign)));
    Vf := Kernel([<2,R![-1, 1]>,<3,R![0, 1]>],Snew);
    return Vf;
end function;