Update mathematical functions (#675)

Document the existing `ROUND`, `CEIL`, and `FLOOR` functions
Also update the trig function docs for searchability

Implement `POW` and `LOG`
Addresses part of #675

Implement ** for integer exponents
** has higher precedence than -, like Python, so -3**4 == -(3**4) == 81

src/asm/lexer.c

@@ -182,6 +182,8 @@ static struct KeywordMapping {
 	{"FLOOR", T_OP_FLOOR},
 	{"DIV", T_OP_FDIV},
 	{"MUL", T_OP_FMUL},
+	{"POW", T_OP_POW},
+	{"LOG", T_OP_LOG},
 	{"SIN", T_OP_SIN},
 	{"COS", T_OP_COS},
 	{"TAN", T_OP_TAN},
@@ -488,7 +490,7 @@ struct KeywordDictNode {
 	uint16_t children[0x60 - ' '];
 	struct KeywordMapping const *keyword;
 /* Since the keyword structure is invariant, the min number of nodes is known at compile time */
-} keywordDict[350] = {0}; /* Make sure to keep this correct when adding keywords! */
+} keywordDict[352] = {0}; /* Make sure to keep this correct when adding keywords! */
 
 /* Convert a char into its index into the dict */
 static inline uint8_t dictIndex(char c)
@@ -1606,13 +1608,20 @@ static int yylex_NORMAL(void)
 		 lexer_GetLineNo(), lexer_GetColNo());
 	for (;;) {
 		int c = nextChar();
+		char secondChar;
 
 		switch (c) {
 		/* Ignore whitespace and comments */
 
 		case '*':
-			if (!lexerState->atLineStart)
+			if (!lexerState->atLineStart) { /* Either MUL or EXP */
+				secondChar = peek(0);
+				if (secondChar == '*') {
+					shiftChars(1);
+					return T_OP_EXP;
+				}
 				return T_OP_MUL;
+			}
 			warning(WARNING_OBSOLETE,
 				"'*' is deprecated for comments, please use ';' instead\n");
 			/* fallthrough */
@@ -1651,7 +1660,6 @@ static int yylex_NORMAL(void)
 			return T_COMMA;
 
 		/* Handle ambiguous 1- or 2-char tokens */
-		char secondChar;
 		case '/': /* Either division or a block comment */
 			secondChar = peek(0);
 			if (secondChar == '*') {