我试图找到特定字符的索引，所以如果字符是＆＃39; d＆＃39;，那么索引就是3
indexOf:
slt $t0, $a2, $t2 #while index of char is <= length
bne $t0, $zero, end2 #if not equal to any letter in string, return -1
addi $a0, $a0, 1 #goes through string
addi $t1, $t1, 1 #add one to t1 for length tracker
j indexOf #looop
end2:
li $v0, -1 #return -1 if char not in string
jr $ra #return to ra