Propagate float/integer type in arithmetic assignment.

Add test.

Mention this and also floating point mod change in README.

ChangeLog

@@ -1,5 +1,8 @@
 2015-01-12  Peter Stephenson  <p.stephenson@samsung.com>
 
+	* 34255: README, Src/math.c, Test/C01arith.ztst: propagate type
+	from variable assignment.  Also note 34230 in README.
+
 	* 34253: Doc/Zsh/contrib.yo: warning on integer arithmetic
 	for zcalc, c.f. 34194.
 

README

@@ -35,6 +35,54 @@ Zsh is a shell with lots of features.  For a list of some of these, see the
 file FEATURES, and for the latest changes see NEWS.  For more
 details, see the documentation.
 
+Incompatibilites between 5.0.7 and 5.0.8
+----------------------------------------
+
+A couple of arithmetic operations have changed: the new behaviour
+is intended to be more consistent, but is not compatible with the old.
+
+Previously, the modulus operation, `%', implicitly converted the
+operation to integer and output an integer result, even if one
+or both of the arguments were floating point.  Now, the C math
+library fmod() operator is used to implement the operation where
+one of the arguments is floating point.  For example:
+
+Old behavour:
+
+% print $(( 5.5 % 2 ))
+1
+
+New behaviour:
+
+% print $(( 5.5 % 2 ))
+1.5
+
+Previously, assignments to variables assigned the correct type to
+variables declared as floating point or integer, but this type was
+not propagated to the value of the expression, as a C programmer
+would naturally expect.  Now, the type of the variable is propagated
+so long as the variable is declared as a numeric type (however this
+happened, e.g. the variable may have been implicitly typed by a
+previous assignment).  For example:
+
+Old behaviour:
+
+% integer var
+% print $(( var = 5.5 / 2.0 ))
+2.2000000000000002
+% print $var
+2
+
+(the actual rounding error may vary).
+
+New behaviour:
+
+% integer var
+% print $(( var = 5.5 / 2.0 ))
+2
+% print $var
+2
+
 Incompatibilities between 5.0.2 and 5.0.5
 -----------------------------------------
 

Src/math.c

@@ -880,6 +880,8 @@ getcvar(char *s)
 static mnumber
 setmathvar(struct mathvalue *mvp, mnumber v)
 {
+    Param pm;
+
     if (mvp->pval) {
 	/*
 	 * This value may have been hanging around for a while.
@@ -909,7 +911,32 @@ setmathvar(struct mathvalue *mvp, mnumber v)
     if (noeval)
 	return v;
     untokenize(mvp->lval);
-    setnparam(mvp->lval, v);
+    pm = setnparam(mvp->lval, v);
+    if (pm) {
+	/*
+	 * If we are performing an assignment, we return the
+	 * number with the same type as the parameter we are
+	 * assigning to, in the spirit of the way assignments
+	 * in C work.  Note this was a change to long-standing
+	 * zsh behaviour.
+	 */
+	switch (PM_TYPE(pm->node.flags)) {
+	case PM_INTEGER:
+	    if (v.type != MN_INTEGER) {
+		v.u.l = (zlong)v.u.d;
+		v.type = MN_INTEGER;
+	    }
+	    break;
+
+	case PM_EFLOAT:
+	case PM_FFLOAT:
+	    if (v.type != MN_FLOAT) {
+		v.u.d = (double)v.u.l;
+		v.type = MN_FLOAT;
+	    }
+	    break;
+	}
+    }
     return v;
 }
 

Test/C01arith.ztst

@@ -16,7 +16,7 @@
   print -- $(( rnd = there * 10000 ))
 # save rounding problems by converting to integer
 0:basic floating point arithmetic
->31415.
+>31415
 
   integer rnd
   (( rnd = ((29.1 % 13.0 * 10) + 0.5) ))
@@ -300,3 +300,11 @@
   print $(( 0b2 ))
 1:Binary numbers don't tend to have 2's in
 ?(eval):1: bad math expression: operator expected at `2 '
+
+  integer varassi
+  print $(( varassi = 5.5 / 2.0 ))
+  print $varassi
+0:Integer variable assignment converts result to integer
+>2
+>2
+# It's hard to test for integer to float.