Merge branch 'master' into freadAtimeStruct

badasahog · web-flow · commit 5f3fccd47b80 · 2025-08-07T18:37:07.000-04:00
diff --git a/NEWS.md b/NEWS.md
@@ -105,6 +105,8 @@
 
 17. `t1 - t2`, where one is an `IDate` and the other is a `Date`, are now consistent with the case where both are `IDate` or both are `Date`, [#4749](https://github.com/Rdatatable/data.table/issues/4749). Thanks @George9000 for the report and @MichaelChirico for the fix.
 
+18. `fwrite` now allows `dec` to be the same as `sep` for edge cases where only one will be written, e.g. 0-row or 1-column tables. [#7227](https://github.com/Rdatatable/data.table/issues/7227). Thanks @MichaelChirico for the report and @venom1204 for the fix.
+
 ### NOTES
 
 1. The following in-progress deprecations have proceeded:
diff --git a/R/data.table.R b/R/data.table.R
@@ -312,7 +312,7 @@ replace_dot_alias = function(e) {
         root = root_name(jsub)
       } else if (length(jsub) > 2L && jsub[[2L]] %iscall% ":=") {
         #2142 -- j can be {} and have length 1
-        stopf("You have wrapped := with {} which is ok but then := must be the only thing inside {}. You have something else inside {} as well. Consider placing the {} on the RHS of := instead; e.g. DT[,someCol:={tmpVar1<-...;tmpVar2<-...;tmpVar1*tmpVar2}]")
+        stopf("Invalid use of `:=` inside `{}`. `:=` must be the only expression inside `{}` when used in `j`. Instead of: DT[{tmp1 <- ...; tmp2 <- ...; someCol := tmp1 * tmp2}], Use: DT[, someCol := {tmp1 <- ...; tmp2 <- ...; tmp1 * tmp2}]")
       }
     }
     if (root=="eval" && !any(all.vars(jsub[[2L]]) %chin% names_x)) {
@@ -2884,7 +2884,7 @@ address = function(x) .Call(Caddress, eval(substitute(x), parent.frame()))
 
 ":=" = function(...) {
   # this error is detected when eval'ing isub and replaced with a more helpful one when using := in i due to forgetting a comma, #4227
-  stopf('Check that is.data.table(DT) == TRUE. Otherwise, :=, `:=`(...) and let(...) are defined for use in j, once only and in particular ways. Note that namespace-qualification like data.table::`:=`(...) is not supported. See help(":=").', class="dt_invalid_let_error")
+  stopf('Check that is.data.table(DT) == TRUE. Otherwise, `:=` is defined for use in j, once only and in particular ways. See help(":=", "data.table"). A common reason for this error is allocating a new column in `j` and using `<-` instead of `:=`; e.g., `DT[, new_col <- 1]` should be `DT[, new_col := 1]`. Another is using `:=` in a multi-statement `{...}` block; please use `:=` as the only statement in `j`.', class="dt_invalid_let_error")
 }
 
 # TODO(#6197): Export these.
diff --git a/R/fwrite.R b/R/fwrite.R
@@ -13,7 +13,8 @@ fwrite = function(x, file="", append=FALSE, quote="auto",
            yaml = FALSE,
            bom = FALSE,
            verbose=getOption("datatable.verbose", FALSE),
-           encoding = "") {
+           encoding = "",
+           forceDecimal = FALSE) {
   na = as.character(na[1L]) # fix for #1725
   if (length(encoding) != 1L || !encoding %chin% c("", "UTF-8", "native")) {
     stopf("Argument 'encoding' must be '', 'UTF-8' or 'native'.")
@@ -44,14 +45,14 @@ fwrite = function(x, file="", append=FALSE, quote="auto",
     is.character(sep) && length(sep)==1L && (nchar(sep) == 1L || identical(sep, "")),
     is.character(sep2) && length(sep2)==3L && nchar(sep2[2L])==1L,
     is.character(dec) && length(dec)==1L && nchar(dec) == 1L,
-    dec != sep,  # sep2!=dec and sep2!=sep checked at C level when we know if list columns are present
+    `dec and sep must be distinct whenever both might be needed` = (!NROW(x) || NCOL(x) <= 1L || dec != sep),  # sep2!=dec and sep2!=sep checked at C level when we know if list columns are present
     is.character(eol) && length(eol)==1L,
     length(qmethod) == 1L && qmethod %chin% c("double", "escape"),
     length(compress) == 1L && compress %chin% c("auto", "none", "gzip"),
     length(compressLevel) == 1L && 0L <= compressLevel && compressLevel <= 9L,
     isTRUEorFALSE(col.names), isTRUEorFALSE(append), isTRUEorFALSE(row.names),
     isTRUEorFALSE(verbose), isTRUEorFALSE(showProgress), isTRUEorFALSE(logical01),
-    isTRUEorFALSE(bom),
+    isTRUEorFALSE(bom), isTRUEorFALSE(forceDecimal),
     length(na) == 1L, #1725, handles NULL or character(0) input
     is.character(file) && length(file)==1L && !is.na(file),
     length(buffMB)==1L && !is.na(buffMB) && 1L<=buffMB && buffMB<=1024L,
@@ -122,7 +123,7 @@ fwrite = function(x, file="", append=FALSE, quote="auto",
   }
   .Call(CfwriteR, x, file, sep, sep2, eol, na, dec, quote, qmethod=="escape", append,
         row.names, col.names, logical01, scipen, dateTimeAs, buffMB, nThread,
-        showProgress, is_gzip, compressLevel, bom, yaml, verbose, encoding)
+        showProgress, is_gzip, compressLevel, bom, yaml, verbose, encoding, forceDecimal)
   invisible()
 }
 
diff --git a/inst/tests/tests.Rraw b/inst/tests/tests.Rraw
@@ -3997,9 +3997,9 @@ test(1133.8, DT[, new := if (.GRP==1L) 7L else 3.4, by=x], data.table(x=INT(1,1,
 DT <- data.table(x=c("A", "A", "B", "B"), val =1:4)
 DT2 <- copy(DT)[, a := 1L]
 test(1134.1, DT[, {a := 1L}], DT2)
-test(1134.2, DT[, {a := 1L; NULL}], error="You have wrapped.*which is ok.*Consider")
+test(1134.2, DT[, {a := 1L; NULL}], error="Invalid use of `:=` inside `{}`")
 test(1134.3, DT[, {b := 2L}, by=x], DT2[, b:=2L, by=x])
-test(1134.4, DT[, {b := 2L; sum(val)}, by=x], error="You have wrapped.*which is ok.*Consider")
+test(1134.4, DT[, {b := 2L; sum(val)}, by=x], error="Invalid use of `:=` inside `{}`")
 
 # FR #2693 and Gabor's suggestions on datatable-help "Problem with FAQ 2.8"
 d1 <- data.table(id1 = c(1L, 2L, 2L, 3L), val = 1:4, key = "id1")
@@ -10977,9 +10977,9 @@ test(1732.7, fwrite(DT, quote='auto'), output='A,B\n,5\nNA,7\n"",0\nmonty,')
 test(1732.8, fwrite(DT, quote='auto', na="NA"), output='A,B\nNA,5\n"NA",7\n"",0\n"monty",NA')
 
 # dec=","
-test(1733.1, fwrite(data.table(pi),dec=","), error=base_messages$stopifnot("dec != sep"))
+# Test 1733.1 removed, see #7227
 test(1733.2, fwrite(data.table(c(1.2,-8.0,pi,67.99),1:4),dec=",",sep=";"),
-           output="V1;V2\n1,2;1\n-8;2\n3,14159265358979;3\n67,99;4")
+             output="V1;V2\n1,2;1\n-8;2\n3,14159265358979;3\n67,99;4")
 
 # fwrite implied and actual row.names
 DT = data.table(foo=1:3,bar=c(1.2,9.8,-6.0))
@@ -21593,3 +21593,30 @@ test(2336.3, all.equal(as.Date(t1) - t2, t1 - t2))
 test(2336.4, all.equal(as.Date(t2) - t1, t2 - t1))
 test(2336.5, all.equal(t1 - as.Date(t2), t1 - t2))
 test(2336.6, all.equal(t2 - as.Date(t1), t2 - t1))
+
+# fwrite: allow dec=',' with single column, #7227
+test(2337.1, fwrite(data.table(1), dec=","), NULL)
+if (getRversion() >= "4.0.0") { # rely on stopifnot(named = ...) for correct message
+  test(2337.2, fwrite(data.table(0.1, 0.2), dec=",", sep=","), error = "dec and sep must be distinct")
+}
+test(2337.3, is.null(fwrite(data.table(c(0.1, 0.2)), dec=",", sep="\t")))
+test(2337.4, is.null(fwrite(data.table(a=numeric(), b=numeric()), dec=",", sep=",")))
+test(2337.5, is.null(fwrite(data.table(a=numeric()), dec=",", sep=",")))
+
+# 2864 force decimal points for whole numbers in numeric columns
+dd = data.table(x=c(1, 2, 3))
+di = data.table(x=c(1L, 2L, 3L))
+test(2338.1, capture.output(fwrite(dd, forceDecimal=TRUE)), c("x", "1.", "2.", "3."))
+test(2338.2, capture.output(fwrite(dd, forceDecimal=TRUE, dec=",", sep="\t")), c("x", "1,", "2,", "3,"))
+test(2338.3, capture.output(fwrite(dd, forceDecimal=FALSE)), c("x", "1", "2", "3"))
+test(2338.4, capture.output(fwrite(di, forceDecimal=TRUE)), c("x", "1", "2", "3"))
+test(2338.5, capture.output(fwrite(data.table(x=c(0.)), forceDecimal=TRUE)), c("x", "0."))
+test(2338.6, capture.output(fwrite(data.table(x=c(-0.)), forceDecimal=TRUE)), c("x", "0."))
+test(2338.7, capture.output(fwrite(data.table(x=c(0.00)), forceDecimal=TRUE)), c("x", "0."))
+# round trip
+local({
+  f <- tempfile(); on.exit(unlink(f))
+  test(2338.8, {fwrite(dd, f, forceDecimal=TRUE); fread(f)}, dd)
+  test(2338.9, {fwrite(dd, f, forceDecimal=FALSE); fread(f)}, di)
+})
+
diff --git a/man/assign.Rd b/man/assign.Rd
@@ -6,6 +6,8 @@
 \description{
     Fast add, remove and update subsets of columns, by reference. \code{:=} operator can be used in two ways: \code{LHS := RHS} form, and \code{Functional form}. See \code{Usage}.
 
+    Note that when using \samp{:=} inside a \code{{...}} block in \code{j}, the \samp{:=} call must be the only statement. For assigning to multiple columns, use the functional form: \code{DT[, `:=`(col1=val1, col2=val2)]}. 
+
     \code{set} is a low-overhead loop-able version of \code{:=}. It is particularly useful for repetitively updating rows of certain columns by reference (using a for-loop). See \code{Examples}. It can not perform grouping operations.
 
     \code{let} is an alias for the functional form and behaves exactly like \code{`:=`}.
@@ -66,7 +68,8 @@ All of the following result in a friendly error (by design) :
     x := 1L
     DT[i, col] := val
     DT[i]$col := val
-    DT[, {col1 := 1L; col2 := 2L}]                # Use the functional form, `:=`(), instead (see above).
+    DT[, {col1 := 1L; col2 := 2L}]                # Using `{}` in `j` is reserved for single `:=` expressions.
+                                                  # For multiple updates, use the functional form `:=`() instead.
 }
 
 For additional resources, please read \href{../doc/datatable-faq.html}{\code{vignette("datatable-faq")}}. Also have a look at StackOverflow's \href{https://stackoverflow.com/questions/tagged/data.table/}{data.table tag}.
diff --git a/man/fwrite.Rd b/man/fwrite.Rd
@@ -21,7 +21,8 @@ fwrite(x, file = "", append = FALSE, quote = "auto",
   yaml = FALSE,
   bom = FALSE,
   verbose = getOption("datatable.verbose", FALSE),
-  encoding = "")
+  encoding = "",
+  forceDecimal = FALSE)
 }
 \arguments{
   \item{x}{Any \code{list} of same length vectors; e.g. \code{data.frame} and \code{data.table}. If \code{matrix}, it gets internally coerced to \code{data.table} preserving col names but not row names}
@@ -62,6 +63,7 @@ fwrite(x, file = "", append = FALSE, quote = "auto",
   \item{bom}{If \code{TRUE} a BOM (Byte Order Mark) sequence (EF BB BF) is added at the beginning of the file; format 'UTF-8 with BOM'.}
   \item{verbose}{Be chatty and report timings?}
   \item{encoding}{ The encoding of the strings written to the CSV file. Default is \code{""}, which means writing raw bytes without considering the encoding. Other possible options are \code{"UTF-8"} and \code{"native"}. }
+  \item{forceDecimal}{ Should decimal points be forced for whole numbers in numeric columns? When \code{FALSE}, the default, whole numbers like \code{c(1.0, 2.0, 3.0)} will be written as \samp{1, 2, 3} i.e., dropping \code{dec}. }
 }
 \details{
 \code{fwrite} began as a community contribution with \href{https://github.com/Rdatatable/data.table/pull/1613}{pull request #1613} by Otto Seiskari. This gave Matt Dowle the impetus to specialize the numeric formatting and to parallelize: \url{https://h2o.ai/blog/2016/fast-csv-writing-for-r/}. Final items were tracked in \href{https://github.com/Rdatatable/data.table/issues/1664}{issue #1664} such as automatic quoting, \code{bit64::integer64} support, decimal/scientific formatting exactly matching \code{write.csv} between 2.225074e-308 and 1.797693e+308 to 15 significant figures, \code{row.names}, dates (between 0000-03-01 and 9999-12-31), times and \code{sep2} for \code{list} columns where each cell can itself be a vector.
diff --git a/src/data.table.h b/src/data.table.h
@@ -319,7 +319,7 @@ SEXP chmatch_R(SEXP, SEXP, SEXP);
 SEXP chmatchdup_R(SEXP, SEXP, SEXP);
 SEXP chin_R(SEXP, SEXP);
 SEXP freadR(SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP);
-SEXP fwriteR(SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP);
+SEXP fwriteR(SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP);
 SEXP rbindlist(SEXP, SEXP, SEXP, SEXP, SEXP);
 SEXP setlistelt(SEXP, SEXP, SEXP);
 SEXP setS4elt(SEXP, SEXP, SEXP);
diff --git a/src/fmelt.c b/src/fmelt.c
@@ -103,12 +103,14 @@ static const char *concat(SEXP vec, SEXP idx) {
 // with missing inputs, and -1 in the positions with column names not
 // found. Column names not found will eventually cause error via
 // uniq_diff().
-SEXP chmatch_na(SEXP x, SEXP table){
-  SEXP ans;
-  PROTECT(ans = chmatch(x, table, -1));
-  for(int i=0; i<length(ans); i++){
-    if(STRING_ELT(x, i) == NA_STRING){
-      INTEGER(ans)[i] = NA_INTEGER;
+SEXP chmatch_na(SEXP x, SEXP table)
+{
+  SEXP ans = chmatch(x, table, -1);
+  PROTECT(ans);
+  int *restrict target = INTEGER(ans);
+  for (int i = 0; i < length(ans); i++) {
+    if (STRING_ELT(x, i) == NA_STRING) {
+      target[i] = NA_INTEGER;
     }
   }
   UNPROTECT(1);
@@ -280,23 +282,23 @@ SEXP checkVars(SEXP DT, SEXP id, SEXP measure, Rboolean verbose) {
 }
 
 struct processData {
-  SEXP RCHK;      // a 2 item list holding vars (result of checkVars) and not_NA_indices. PROTECTed up in fmelt so that preprocess() doesn't need to PROTECT. To pass rchk, #2865
-  SEXP idcols,    // convenience pointers into RCHK[0][0], RCHK[0][1] and RCHK[1] respectively
-    variable_table, // NULL or data for variable column(s).
-    valuecols,    // list with one element per output/value column, each element is an integer vector.
-    not_NA_indices;
-  int *isfactor,
-    *leach,       // length of each element of the valuecols(measure.vars) list.
-    *isidentical; // are all inputs for this value column the same type?
-  int lids,       // number of id columns.
-    lvars,        // number of variable columns.
-    lvalues,      // number of value columns.
-    lmax,         // max length of valuecols elements / number of times to repeat ids.
-    totlen,       // of output/long DT result of melt operation.
-    nrow;         // of input/wide DT to be melted.
+  SEXP RCHK;           // a 2 item list holding vars (result of checkVars) and not_NA_indices. PROTECTed up in fmelt so that preprocess() doesn't need to PROTECT. To pass rchk, #2865
+  SEXP idcols;         // convenience pointers into RCHK[0][0], RCHK[0][1] and RCHK[1] respectively
+  SEXP variable_table; // NULL or data for variable column(s).
+  SEXP valuecols;      // list with one element per output/value column, each element is an integer vector.
+  SEXP not_NA_indices;
+  int *isfactor;
+  int *leach;          // length of each element of the valuecols(measure.vars) list.
+  int *isidentical;    // are all inputs for this value column the same type?
+  int lids;            // number of id columns.
+  int lvars;           // number of variable columns.
+  int lvalues;         // number of value columns.
+  int lmax;            // max length of valuecols elements / number of times to repeat ids.
+  int totlen;          // of output/long DT result of melt operation.
+  int nrow;            // of input/wide DT to be melted.
   SEXPTYPE *maxtype;
-  bool measure_is_list,
-    narm;  // remove missing values?
+  bool measure_is_list;
+  bool narm;           // remove missing values?
 };
 
 static void preprocess(SEXP DT, SEXP id, SEXP measure, SEXP varnames, SEXP valnames, Rboolean narm, Rboolean verbose, struct processData *data) {
diff --git a/src/frank.c b/src/frank.c
@@ -3,22 +3,26 @@
 // #include <signal.h> // the debugging machinery + breakpoint aidee
 // raise(SIGINT);
 
-SEXP dt_na(SEXP x, SEXP cols) {
-  int n=0, elem;
-
+SEXP dt_na(SEXP x, SEXP cols)
+{
   if (!isNewList(x)) internal_error(__func__, "Argument '%s' to %s is type '%s' not '%s'", "x", "Cdt_na", type2char(TYPEOF(x)), "list"); // # nocov
   if (!isInteger(cols)) internal_error(__func__, "Argument '%s' to %s is type '%s' not '%s'", "cols", "Cdt_na", type2char(TYPEOF(cols)), "integer"); // # nocov
-  for (int i=0; i<LENGTH(cols); ++i) {
-    elem = INTEGER(cols)[i];
-    if (elem<1 || elem>LENGTH(x))
-      error(_("Item %d of 'cols' is %d which is outside 1-based range [1,ncol(x)=%d]"), i+1, elem, LENGTH(x));
-    if (!n) n = length(VECTOR_ELT(x, elem-1));
+
+  int n = 0;
+  const int numCols = LENGTH(cols);
+  const int* col_ints = INTEGER_RO(cols);
+  for (int i = 0; i < numCols; i++) {
+    const int elem = col_ints[i];
+    if (elem < 1 || elem > LENGTH(x))
+      error(_("Item %d of 'cols' is %d which is outside 1-based range [1,ncol(x)=%d]"), i + 1, elem, LENGTH(x));
+    if (!n) n = length(VECTOR_ELT(x, elem - 1));
   }
   SEXP ans = PROTECT(allocVector(LGLSXP, n));
   int *ians = LOGICAL(ans);
-  for (int i=0; i<n; ++i) ians[i]=0;
-  for (int i=0; i<LENGTH(cols); ++i) {
-    SEXP v = VECTOR_ELT(x, INTEGER(cols)[i]-1);
+  memset(ians, 0, n * sizeof(int));
+
+  for (int i = 0; i < numCols; i++) {
+    SEXP v = VECTOR_ELT(x, col_ints[i]-1);
     if (!length(v) || isList(v)) continue; // like stats:::na.omit.data.frame, skip pairlist columns
     if (n != length(v))
       error(_("Column %d of input list x is length %d, inconsistent with first column of that item which is length %d."), i+1,length(v),n);
diff --git a/src/freadR.c b/src/freadR.c
@@ -265,15 +265,13 @@ bool userOverride(int8_t *type, lenOff *colNames, const char *anchor, const int
   colNamesSxp = R_NilValue;
   SET_VECTOR_ELT(RCHK, 1, colNamesSxp = allocVector(STRSXP, ncol));
   for (int i = 0; i < ncol; i++) {
-    SEXP elem;
     if (colNames == NULL || colNames[i].len <= 0) {
       char buff[12];
       snprintf(buff, sizeof(buff), "V%d", i + 1); // # notranslate
-      elem = mkChar(buff);  // no PROTECT as passed immediately to SET_STRING_ELT
+      SET_STRING_ELT(colNamesSxp, i, mkChar(buff));  // no PROTECT as passed immediately to SET_STRING_ELT
     } else {
-      elem = mkCharLenCE(anchor + colNames[i].off, colNames[i].len, ienc);  // no PROTECT as passed immediately to SET_STRING_ELT
+      SET_STRING_ELT(colNamesSxp, i, mkCharLenCE(anchor + colNames[i].off, colNames[i].len, ienc));  // no PROTECT as passed immediately to SET_STRING_ELT
     }
-    SET_STRING_ELT(colNamesSxp, i, elem);
   }
   // "use either select= or drop= but not both" was checked earlier in freadR
   applyDrop(dropSxp, type, ncol, /*dropSource=*/-1);
diff --git a/src/fwrite.c b/src/fwrite.c
@@ -42,6 +42,7 @@ static int scipen;
 static bool squashDateTime=false;      // 0=ISO(yyyy-mm-dd) 1=squash(yyyymmdd)
 static bool verbose=false;
 static int gzip_level;
+static bool forceDecimal=false;       // force writing decimal points for numeric columns
 
 extern const char *getString(const void *, int64_t);
 extern int getStringLen(const void *, int64_t);
@@ -198,6 +199,9 @@ void writeFloat64(const void *col, int64_t row, char **pch)
     }
   } else if (x == 0.0) {
     *ch++ = '0';   // and we're done.  so much easier rather than passing back special cases
+    if (forceDecimal) {
+      *ch++ = dec;
+    }
   } else {
     if (x < 0.0) { *ch++ = '-'; x = -x; }  // and we're done on sign, already written. no need to pass back sign
     union { double d; uint64_t l; } u;
@@ -237,8 +241,13 @@ void writeFloat64(const void *col, int64_t row, char **pch)
     if (l % 10 >= 5) l += 10; // use the last digit to round
     l /= 10;
     if (l == 0) {
+      // # nocov start. Very likely not needed as such numbers (e.g. 2^-1075) likely not representable in R.
       if (*(ch - 1) == '-') ch--;
       *ch++ = '0';
+      if (forceDecimal) {
+        *ch++ = dec;
+      }
+      // # nocov end
     } else {
       // Count trailing zeros and therefore s.f. present in l
       int trailZero = 0;
@@ -257,6 +266,10 @@ void writeFloat64(const void *col, int64_t row, char **pch)
         if (sf > dr) width = sf + 1;                     // 1.234 and 123.4
         else { dl0 = 1; width = dr + 1 + dl0; }            // 0.1234, 0.0001234
       }
+      const bool isWholeNumber = (dr == 0 && dl0 >= 0);
+      if (forceDecimal && isWholeNumber) { 
+        width += 1; 
+      }
       // So:  3.1416 => l=31416, sf=5, exp=0     dr=4; dl0=0; width=6
       //      30460  => l=3046, sf=4, exp=4      dr=0; dl0=1; width=5
       //      0.0072 => l=72, sf=2, exp=-3       dr=4; dl0=1; width=6
@@ -269,6 +282,8 @@ void writeFloat64(const void *col, int64_t row, char **pch)
           while (dr && sf) { *ch-- = '0' + l % 10; l /= 10; dr--; sf--; }
           while (dr) { *ch-- = '0'; dr--; }
           *ch-- = dec;
+        } else if (forceDecimal && isWholeNumber) {
+          *ch-- = dec;
         }
         while (dl0) { *ch-- = '0'; dl0--; }
         while (sf) { *ch-- = '0' + l % 10; l /= 10; sf--; }
@@ -615,6 +630,7 @@ void fwriteMain(fwriteMainArgs args)
   int8_t quoteHeaders = args.doQuote;
   verbose = args.verbose;
   gzip_level = args.gzip_level;
+  forceDecimal = args.forceDecimal;
 
   size_t len;
   unsigned int crc;
diff --git a/src/fwrite.h b/src/fwrite.h
diff --git a/src/fwriteR.c b/src/fwriteR.c
diff --git a/src/idatetime.c b/src/idatetime.c
diff --git a/src/nqrecreateindices.c b/src/nqrecreateindices.c
diff --git a/src/quickselect.c b/src/quickselect.c

Original file line number	Diff line number	Diff line change
`@@ -312,7 +312,7 @@ replace_dot_alias = function(e) {`
`312`	`312`	`root = root_name(jsub)`
`313`	`313`	`} else if (length(jsub) > 2L && jsub[[2L]] %iscall% ":=") {`
`314`	`314`	`#2142 -- j can be {} and have length 1`
`315`		`- stopf("You have wrapped := with {} which is ok but then := must be the only thing inside {}. You have something else inside {} as well. Consider placing the {} on the RHS of := instead; e.g. DT[,someCol:={tmpVar1<-...;tmpVar2<-...;tmpVar1*tmpVar2}]")`
	`315`	+ stopf("Invalid use of `:=` inside `{}`. `:=` must be the only expression inside `{}` when used in `j`. Instead of: DT[{tmp1 <- ...; tmp2 <- ...; someCol := tmp1 * tmp2}], Use: DT[, someCol := {tmp1 <- ...; tmp2 <- ...; tmp1 * tmp2}]")
`316`	`316`	`}`
`317`	`317`	`}`
`318`	`318`	`if (root=="eval" && !any(all.vars(jsub[[2L]]) %chin% names_x)) {`
`@@ -2884,7 +2884,7 @@ address = function(x) .Call(Caddress, eval(substitute(x), parent.frame()))`
`2884`	`2884`
`2885`	`2885`	`":=" = function(...) {`
`2886`	`2886`	`# this error is detected when eval'ing isub and replaced with a more helpful one when using := in i due to forgetting a comma, #4227`
`2887`		- stopf('Check that is.data.table(DT) == TRUE. Otherwise, :=, `:=`(...) and let(...) are defined for use in j, once only and in particular ways. Note that namespace-qualification like data.table::`:=`(...) is not supported. See help(":=").', class="dt_invalid_let_error")
	`2887`	+ stopf('Check that is.data.table(DT) == TRUE. Otherwise, `:=` is defined for use in j, once only and in particular ways. See help(":=", "data.table"). A common reason for this error is allocating a new column in `j` and using `<-` instead of `:=`; e.g., `DT[, new_col <- 1]` should be `DT[, new_col := 1]`. Another is using `:=` in a multi-statement `{...}` block; please use `:=` as the only statement in `j`.', class="dt_invalid_let_error")
`2888`	`2888`	`}`
`2889`	`2889`
`2890`	`2890`	`# TODO(#6197): Export these.`