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Fixes for the ToRational statement. #787

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Merged
jodavies merged 1 commit into from
Jan 27, 2026
Merged

Fixes for the ToRational statement. #787

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67 changes: 67 additions & 0 deletions check/features.frm
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Original file line number Diff line number Diff line change
Expand Up @@ -1463,6 +1463,73 @@ assert result("ATANH") =~ expr("
- 6.08698087464190136361e-01*atanh( - 5.4321e-01)
")
*--#] evaluate_atanh :
*--#[ torat :
#-
#StartFloat 16d
Symbol a,b,jj;
Local F1 = 0.0
-10^-20*a
+1023/1024*a^2
-17/1024*a^3
+3602879701896397/2^55*a^4
-10^20*a^5
+17*a^6
;
Local F2 = sum_(jj,1,16,(355/113+10^-jj)*a^jj);
Local F3 = 0.3*a^1+0.33*a^2+0.333*a^3+0.3333*a^4+0.33333*a^5+0.333333*a^6+0.3333333*a^7+0.33333333*a^8+0.333333333*a^9+0.3333333333*a^10+0.33333333333*a^11+0.333333333333*a^12+0.3333333333333*a^13+0.33333333333333*a^14+0.333333333333333*a^15+0.3333333333333333*a^16;
ToFloat;
.sort

ToRat;
.sort

#StartFloat 50d
Local F4 = 10e-20;
ToRat;
Print +s;
.end
#pend_if wordsize == 2
assert succeeded?
assert result("F1") =~ expr("+ 1023/1024*a^2
- 17/1024*a^3
+ 1/10*a^4
- 100000000000000000000*a^5
+ 17*a^6")
assert result("F2") =~ expr("+ 3663/1130*a
+ 35613/11300*a^2
+ 355113/113000*a^3
+ 3550113/1130000*a^4
+ 35500113/11300000*a^5
+ 355000113/113000000*a^6
+ 2205176720676/701929469027*a^7
+ 5798543718053/1845733628322*a^8
+ 4781671236789/1522053097423*a^9
+ 492368235747/156725663768*a^10
+ 355/113*a^11
+ 355/113*a^12
+ 355/113*a^13
+ 355/113*a^14
+ 355/113*a^15
+ 355/113*a^16")
assert result("F3") =~ expr("
+ 3/10*a
+ 33/100*a^2
+ 333/1000*a^3
+ 3333/10000*a^4
+ 33333/100000*a^5
+ 333333/1000000*a^6
+ 3333333/10000000*a^7
+ 33333333/100000000*a^8
+ 1/3*a^9
+ 1/3*a^10
+ 1/3*a^11
+ 1/3*a^12
+ 1/3*a^13
+ 1/3*a^14
+ 1/3*a^15
+ 1/3*a^16")
assert result("F4") =~ expr("+ 1/10000000000000000000")
*--#] torat :
*--#[ strictrounding_1 :
#StartFloat 6d
CFunction f;
Expand Down
27 changes: 18 additions & 9 deletions sources/float.c
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Original file line number Diff line number Diff line change
Expand Up @@ -591,7 +591,7 @@ long FloatToInteger(UWORD *out, mpf_t floatin, long *bitsused)
mpz_set_f(z,floatin);
ZtoForm(out,&nout,z);
mpz_clear(z);
x = out[0]; nx = 0;
x = out[nout-1]; nx = 0;
while ( x ) { nx++; x >>= 1; }
*bitsused = (nout-1)*BITSINWORD + nx;
return(nout);
Expand Down Expand Up @@ -678,7 +678,7 @@ int FloatToRat(UWORD *ratout, WORD *nratout, mpf_t floatin)
WORD na, nb, nc, nd, i;
int nout;
LONG oldpWorkPointer = AT.pWorkPointer;
long bitsused = 0, totalbitsused = 0, totalbits = AC.DefaultPrecision;
long bitsused = 0, totalbitsused = 0, totalbits = AC.DefaultPrecision-AC.MaxWeight-1;
int retval = 0, startnul;
WantAddPointers(AC.DefaultPrecision); /* Horrible overkill */
AT.pWorkSpace[AT.pWorkPointer++] = out;
Expand Down Expand Up @@ -710,15 +710,24 @@ int FloatToRat(UWORD *ratout, WORD *nratout, mpf_t floatin)
else {
nout = FloatToInteger((UWORD *)out,aux1,&bitsused);
out += nout;
totalbitsused += bitsused;
}
if ( bitsused > (totalbits-totalbitsused)/2 ) { break; }
if ( mpf_sgn(aux2) == 0 ) {
/*if ( startnul == 1 )*/ AT.pWorkSpace[AT.pWorkPointer++] = out;
break;
}
totalbitsused += bitsused;
AT.pWorkSpace[AT.pWorkPointer++] = out;
}
/*
For |floatin| << 1, we have startnul = 1 and hit the precision guard
already on the first continued-fraction step. The resulting float is
therefore close to the rational 0/1 and we can immediately return.
*/
if ( startnul == 1 && AT.pWorkPointer == oldpWorkPointer + 2 ) {
*ratout++ = 0; *ratout++ = 1; *ratout = *nratout = 3;
goto ret;
}
/*
At this point we have the function with the repeated fraction.
Now we should work out the fraction. Form code would be:
Expand All @@ -734,11 +743,6 @@ int FloatToRat(UWORD *ratout, WORD *nratout, mpf_t floatin)
na = 1; a[0] = 1;
c = (UWORD *)(AT.pWorkSpace[--AT.pWorkPointer]);
nc = nb = ((UWORD *)out)-c;
if ( nc > 10 ) {
mc = c;
c = (UWORD *)(AT.pWorkSpace[--AT.pWorkPointer]);
nc = nb = ((UWORD *)mc)-c;
}
for ( i = 0; i < nb; i++ ) b[i] = c[i];
mc = c = NumberMalloc("FloatToRat");
while ( AT.pWorkPointer > oldpWorkPointer ) {
Expand Down Expand Up @@ -791,12 +795,13 @@ int FloatToRat(UWORD *ratout, WORD *nratout, mpf_t floatin)
if ( s < 0 ) mpf_neg(floatin,floatin);
/*
{
WORD n = *ratout;
WORD n = *nratout;
RatToFloat(aux1,ratout,n);
mpf_sub(aux2,floatin,aux1);
gmp_printf("Diff is %.*Fe\n",40,aux2);
}
*/
ret:
return(retval);
}

Expand Down Expand Up @@ -1492,7 +1497,11 @@ int ToRat(PHEAD WORD *term, WORD level)
The result can go straight over the float_ function.
*/
UnpackFloat(aux4,t);
// If aux4 is zero, the term vanishes
if ( mpf_sgn(aux4) == 0 ) return(0);
if ( FloatToRat((UWORD *)t,&ncoef,aux4) == 0 ) {
// Check if the resulting rational is zero
if ( t[0] == 0 && t[1] == 1 && ncoef == 3 ) return(0);
t += ABS(ncoef);
t[-1] = ncoef*nsign;
*term = t - term;
Expand Down
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