several more stubs for math routines

c64/basic/,stubs_math/bf7b.FPWRT.s

@@ -0,0 +1,24 @@
+// #LAYOUT# STD *       #TAKE
+// #LAYOUT# *   BASIC_0 #TAKE
+// #LAYOUT# *   *       #IGNORE
+
+//
+// Math package - set FAC1 as FAC2 raised to the power of FAC1
+//
+// Input:
+// - .A - must load FAC1 exponent ($61) beforehand to set the zero flag
+//
+// Note:
+// - load FAC2 after FAC1, or mimic the Kernals sign comparison
+// - uses exp(x*log(y)) formula to calculate y^x; slow and inaccurate
+//
+// See also:
+// - [CM64] Computes Mapping the Commodore 64 - page 117
+// - https://www.c64-wiki.com/wiki/Floating_point_arithmetic
+// - https://codebase64.org/doku.php?id=base:kernal_floating_point_mathematics
+//
+
+// XXX provide implementation
+
+FPWRT:
+	STUB_IMPLEMENTATION()