Add STRSTARTS and STRENDS functions (#2159)

man/rgbasm.5

@@ -653,12 +653,14 @@ The following functions take varying operands, and return strings:
 .El
 .Pp
 The following functions operate on string expressions, but return integers:
-.Bl -column "STRRFIND(str, sub)"
+.Bl -column "STRSTARTS(str, prefix)"
 .It Sy Name Ta Sy Operation
 .It Fn STRLEN str Ta Returns the number of characters in Ar str .
 .It Fn STRCMP str1 str2 Ta Compares Ar str1 No and Ar str2 No according to ASCII ordering of their characters. Returns -1 if Ar str1 No is lower than Ar str2 Ns , 1 if Ar str1 No is greater than Ar str2 Ns , or 0 if they match.
 .It Fn STRFIND str sub Ta Returns the first index of Ar sub No in Ar str Ns , or -1 if it's not present.
 .It Fn STRRFIND str sub Ta Returns the last index of Ar sub No in Ar str Ns , or -1 if it's not present.
+.It Fn STRSTARTS str prefix Ta Returns 1 if Ar str No starts with Ar prefix Ns , or 0 otherwise.
+.It Fn STRENDS str suffix Ta Returns 1 if Ar str No ends with Ar suffix Ns , or 0 otherwise.
 .It Fn BYTELEN str Ta Returns the number of bytes in Ar str . Pq Non-ASCII characters can be multiple bytes.
 .It Fn STRBYTE str idx Ta Returns the byte value at Ar idx No in Ar str .
 .It Fn INCHARMAP str Ta Returns 1 if Ar str No has an entry in the current charmap, or 0 otherwise.