func (st *state) checkChar(c byte) {
	if len(st.str) == 0 || st.str[0] != c {
		panic("internal error")
	}
	st.advance(1)
}
func (st *state) checkChar(c byte) {
	if len(st.str) == 0 || st.str[0] != c {
		panic("internal error")
	}
	st.advance(1)
}
func ( st * state ) checkChar ( c byte ) { if len ( st . str ) == 0 || st . str [ 0 ] != c { panic ( " " ) } st . advance ( 1 ) }
// checkChar requires that the next character in the string be c, and
// advances past it.
checkChar requires that the next character in the string be c and advances past it .