Convert a trinary number, represented as a string (e.g. '102012'), to its decimal equivalent using first principles.
The program should consider strings specifying an invalid trinary as the value 0.
Trinary numbers contain three symbols: 0, 1, and 2.
The last place in a trinary number is the 1's place. The second to last is the 3's place, the third to last is the 9's place, etc.
# "102012" 1 0 2 0 1 2 # the number 1*3^5 + 0*3^4 + 2*3^3 + 0*3^2 + 1*3^1 + 2*3^0 # the value 243 + 0 + 54 + 0 + 3 + 2 = 302
If your language provides a method in the standard library to perform the conversion, pretend it doesn't exist and implement it yourself.
All of Computer Science http://www.wolframalpha.com/input/?i=binary&a=*C.binary-_*MathWorld-
It's possible to submit an incomplete solution so you can see how others have completed the exercise.
# # Test trinary_convert with some examples # # s0 - num of tests left to run # s1 - address of input word # s2 - address of expected output word # s3 - char byte # s4 - output word # # trinary_convert must: # - be named trinary_convert and declared as global # - read input address of string from a0 # - follow the convention of using the t0-9 registers for temporary storage # - (if it uses s0-7 then it is responsible for pushing existing values to the stack then popping them back off before returning) # - write integer result to v0 .data # number of test cases n: .word 6 # input values (null terminated) & expected output values (word sized ints) ins: .asciiz "0", "1", "10", "102101", "22222", "10000" outs: .word 0, 1, 3, 307, 242, 81 failmsg: .asciiz "failed for test input: " okmsg: .asciiz "all tests passed" .text runner: lw $s0, n la $s1, ins la $s2, outs run_test: move $a0, $s1 # move address of input str to a0 jal trinary_convert # call subroutine under test move $v1, $v0 # move return value in v0 to v1 because we need v0 for syscall lw $s4, 0($s2) # read expected output from memory bne $v1, $s4, exit_fail # if expected doesn't match actual, jump to fail scan: addi $s1, $s1, 1 # move input address on byte forward lb $s3, 0($s1) # load byte beq $s3, $zero, done_scan # if char null, break loop j scan # loop done_scan: addi $s1, $s1, 1 # move input address on byte past null addi $s2, $s2, 4 # move to next word in output sub $s0, $s0, 1 # decrement num of tests left to run bgt $s0, $zero, run_test # if more than zero tests to run, jump to run_test exit_ok: la $a0, okmsg # put address of okmsg into a0 li $v0, 4 # 4 is print string syscall li $v0, 10 # 10 is exit with zero status (clean exit) syscall exit_fail: la $a0, failmsg # put address of failmsg into a0 li $v0, 4 # 4 is print string syscall move $a0, $s1 # print input that failed on li $v0, 4 syscall li $a0, 1 # set error code to 1 li $v0, 17 # 17 is exit with error syscall # # Include your implementation here if you wish to run this from the MARS GUI. # .include "impl.mips"
# read a string representation of a ternary number and # return its integer equivalent # a0::String -> v0::Signed trinary_convert: li $v0, 0 loop: lb $t0, 0($a0) beq $t0, $0, return addi $a0, $a0, 1 sll $t1, $v0, 1 add $v0, $v0, $t1 addi $t0, $t0, -48 bltz $t0, fail # below the '0' - '2' range addi $t1, $t0, -3 bgez $t1, fail # above the '0' - '2' range add $v0, $v0, $t0 b loop fail: li $v0, -1 return: jr $ra
A huge amount can be learned from reading other people’s code. This is why we wanted to give exercism users the option of making their solutions public.
Here are some questions to help you reflect on this solution and learn the most from it.