From dcb010fdfbc7dac48197d71a504a0ab71878c03c Mon Sep 17 00:00:00 2001
From: Henry Rich <henryhrich@gmail.com>
Date: Sat, 11 Jan 2025 14:32:26 -0500
Subject: [PATCH] '-' sign in ":!.20 qp; leading - sign lost from _0.1fq; crash
 in 0j_1 ": 0fq

---
 jsrc/f.c    |  3 ++-
 jsrc/f2.c   |  7 ++++++-
 jsrc/wn.c   |  7 +++----
 test/gj.ijs | 13 +++++++++++++
 4 files changed, 24 insertions(+), 6 deletions(-)

diff --git a/jsrc/f.c b/jsrc/f.c
index 3d5bd8b6c..93f1ddd77 100644
--- a/jsrc/f.c
+++ b/jsrc/f.c
@@ -147,6 +147,7 @@ struct fmtbuf fmtlong(struct fmtbuf fb, E v){
  finish:;
  if(ndig!=0&&buf[0]==0){++buf; --dp; --ndig;}  // if we added a lead 0 and it is still there, remove it
  DO(ndig, buf[i]+='0';)  // convert the digits to chars
+ dp=ndig==0?1:dp;  // if there are no digits, input must be 0; set decimal point to 1 to match 0. display
  R (struct fmtbuf){buf,fbuf,ndig,dp};
 }
 
@@ -161,7 +162,7 @@ static FMTF(jtfmtE,E){UI i;
  // copy result to output area
  I endx0=MIN(r.ndig,jt->ppn);  // discard excess significance
  I exp0=r.dp;  // number of digits of sig before decimal point.  Can be neg
- s[0]='-'; I sgn0=v->hi<0;  // install - sign just in case; set sgn0 to be # chars of sign needed
+ s[0]='_'; I sgn0=v->hi<0;  // install - sign just in case; set sgn0 to be # chars of sign needed
  if(BETWEENC(exp0,0,endx0)){
   // decimal point within significance: report as decimal
   if(exp0==0)s[sgn0++]='0';  // if no digits before decimal point, add one and add it to count of sign chars
diff --git a/jsrc/f2.c b/jsrc/f2.c
index 3c59006e6..612f46990 100644
--- a/jsrc/f2.c
+++ b/jsrc/f2.c
@@ -215,7 +215,12 @@ static B jtfmte(J jt,B e,I m,I d,C*s,I t,E*wv,A*cellbuf){
  C *z=CAV(*cellbuf);  // place to build result, which is known to fit
  z[0]=' '; z+=s[0]==' '; z[0]='_'; z+=wv->hi<0;   // advance s past optional leading space and sign 
  if(e){  // %e field, scientific
-  *z++=fmt.buf[0]; if(wdec){*z++='.'; I nfrac=MIN(fmt.ndig-1,wfrac); MC(z,&fmt.buf[1],nfrac); if(unlikely(nfrac<wfrac))mvc(wfrac-nfrac,&z[nfrac],1,"0"); z+=wfrac;}  // move sig digits
+  *z++=fmt.ndig?fmt.buf[0]:'0';  // the digit before decimal point: first digit, but '0' if there are no digits
+  if(wdec){  // if we should display after the decimal point...
+   *z++='.'; I nfrac=MIN(MAX(fmt.ndig,1)-1,wfrac); MC(z,&fmt.buf[1],nfrac);  // move sig digits.  nfrac is # digits left after the (possible) first
+   if(unlikely(nfrac<wfrac))mvc(wfrac-nfrac,&z[nfrac],1,"0");  // extend with 0s if needed
+   z+=wfrac;  // step over all moved digits, to exponent location
+  }
   *z++='e'; z[0]='_'; z+=(exp<0); sprintf(z,"%d",ABS((int)exp));  // move exponent incl trailing NUL
  }else{  // decimal point
   if(fmt.dp>0){MC(z,&fmt.buf[0],fmt.dp); z+=fmt.dp;}else *z++='0';  // if there are integer digits, move them; if not lead with 0.  Advance z to frac
diff --git a/jsrc/wn.c b/jsrc/wn.c
index fe501e18b..028178792 100644
--- a/jsrc/wn.c
+++ b/jsrc/wn.c
@@ -84,15 +84,14 @@ static NUMH(jtnumfq){E *v;D sgn=1.0;
  else if(i<n){R 0;}
  // negative exponent; need to make a rational
  if(ex<0){
-  // underflow
-  if(unlikely(ex<-400)){v->hi=v->lo=0*sgn;R 1;}
+  if(unlikely(ex<-400)){v->hi=v->lo=0*sgn;R 1;} // underflow
   RZ(qquad(v,qtymes(((Q){.n=r,.d=X1}),((Q){.n=X1,.d=xpow(xc(10),xc(-ex))}))));}
  else{
   if(ex){
-   // overflow
-   if(unlikely(ex>400)){v->hi=inf*sgn;R 1;}
+   if(unlikely(ex>400)){v->hi=inf*sgn;R 1;}// overflow
    r=xtymes(r,xpow(xc(10),xc(ex)));}
   RZ(xquad(v,r));}
+ v->hi*=sgn; v->lo*=sgn;  // install sign, which does not upset canonical form
  R 1;}
 
 static NUMH(jtnumj){C*t,*ta;D x,y;Z*v;
diff --git a/test/gj.ijs b/test/gj.ijs
index f12aee4d8..516b84619 100644
--- a/test/gj.ijs
+++ b/test/gj.ijs
@@ -268,6 +268,19 @@ a =: 1 +&(11&c.) 1e_20
 
 '1.000000000000000000000000000000' -: 0j30 ": (*%) 11 c. 665142606648569600281099799288x
 
+'1.000000000000000039' -: ":!.20[1.00000000000000004fq
+(,'1') -: ":[1.00000000000000004fq
+'_1.000000000000000039' -: ":!.20[_1.00000000000000004fq
+(,'_1') -: ":[_1.00000000000000004fq
+(,'_3.99999999999999991e_17') -: ":!.20[_0.00000000000000004fq
+('3.99999999999999991e_17') -: ":!.20[0.00000000000000004fq
+
+'0.0e0' -: 0j_1 ": 0fq
+'0.00e0' -: 0j_2 ": 0fq
+'5.00e_1' -: 0j_2 ": 0.5fq
+'_5.00e_1' -: 0j_2 ": _0.5fq
+
+
 NB. qx =: 11 c. 665142606648569600281099799288x
 NB. qy =: 11 c. 665142606648569600281099799280x
 NB. t =: 9!:12