FIX: log-* functions should not return positive number required errors

fixes: Oldes/Rebol-issues#2432

Author: Oldes

src/core/n-math.c

@@ -352,7 +352,9 @@ enum {SINE, COSINE, TANGENT};
 ***********************************************************************/
 {
 	REBDEC dval = AS_DECIMAL(D_ARG(1));
+#ifdef USE_NO_INFINITY
 	if (dval <= 0) Trap0(RE_POSITIVE);
+#endif
 	SET_DECIMAL(D_RET, log10(dval));
 	return R_RET;
 }
@@ -365,7 +367,9 @@ enum {SINE, COSINE, TANGENT};
 ***********************************************************************/
 {
 	REBDEC dval = AS_DECIMAL(D_ARG(1));
+#ifdef USE_NO_INFINITY
 	if (dval <= 0) Trap0(RE_POSITIVE);
+#endif
 	SET_DECIMAL(D_RET, log(dval) / LOG2);
 	return R_RET;
 }
@@ -378,7 +382,9 @@ enum {SINE, COSINE, TANGENT};
 ***********************************************************************/
 {
 	REBDEC dval = AS_DECIMAL(D_ARG(1));
+#ifdef USE_NO_INFINITY
 	if (dval <= 0) Trap0(RE_POSITIVE);
+#endif
 	SET_DECIMAL(D_RET, log(dval));
 	return R_RET;
 }

src/tests/units/decimal-test.r3

@@ -125,6 +125,28 @@ Rebol [
 ===end-group===
 
 
+===start-group=== "log"
+	--test-- "log-* -1"
+		;@@ https://github.com/Oldes/Rebol-issues/issues/2431
+		--assert "1.#NaN" = mold try [log-2  -1]
+		--assert "1.#NaN" = mold try [log-e  -1]
+		--assert "1.#NaN" = mold try [log-10 -1]
+		
+	--test-- "log-* 0"
+		--assert "-1.#INF" = mold try [log-2  0]
+		--assert "-1.#INF" = mold try [log-e  0]
+		--assert "-1.#INF" = mold try [log-10 0]
+
+	--test-- "log-2 32"
+		--assert 5.0 = log-2 32
+	--test-- "log-10 100"
+		--assert 2.0 = log-10 100
+	--test-- "log-e 123"
+		--assert 4.812184355372417 = log-e 123
+
+===end-group===
+
+
 ===start-group=== "decimal issues"
 	--test-- "issue-1753"
 	;@@ https://github.com/Oldes/Rebol-issues/issues/1753