Name: Anonymous 2010-03-18 23:17
I'm having trouble writing a method that removes all characters from a string that aren't letters or integers. What happens is that as soon as a character designated to be set to null is encountered, all characters that follow are set to null too.
Any help would be appreciated.
.data
Buffer: .asciiz " " # 80 bytes in Buffer
intro: .asciiz "Hello, please enter a string of up to 80 characters. I will then tell you if that string was a palindrome!"
.text
main:
li $v0, 4 # print_string call number
la $a0, intro # pointer to string in memory
syscall
li $v0, 8 #syscall code for reading string
la $a0, Buffer #save read string into buffer
li $a1, 80 #string is 80 bytes long
syscall
li $s0, 0 #i = 0
li $t0, 80 #max for i to reach
la $a0, Buffer
jal stripNonAlpha
li $v0, 4 # print_string call number
la $a0, Buffer # pointer to string in memory
syscall
#################################
# stripNonAlpha method #
#################################
stripNonAlpha:
beq $s0, $t0, stripEnd #if i = 80 end
add $t4, $s0, $a0 #address of Buffer[i] in $t4
lb $s1, 0($t4) #load value of Buffer[i]
slti $t1, $s1, 48 #if ascii code is less than 48
bne $t1, $zero, strip #remove ascii character
slti $t1, $s1, 58 #if ascii code is greater than 57
#and
slti $t2, $s1, 65 #if ascii code is less than 65
slt $t3, $t1, $t2
bne $t3, $zero, strip #remove ascii character
slti $t1, $s1, 91 #if ascii code is greater than 90
#and
slti $t2, $s1, 97 #if ascii code is less than 97
slt $t3, $t1, $t2
bne $t3, $zero, strip #remove ascii character
slti $t1, $s1, 123 #if ascii character is greater than 122
beq $t1, $zero, strip #remove ascii character
addi $s0, $s0, 1 #i = i + 1
j stripNonAlpha #go to stripNonAlpha
strip:
add $t5, $s0, $a0 #address of Buffer[i] in $t5
sb $0, 0($t5) #Buffer[i] = 0
addi $s0, $s0, 1 #i = i + 1
j stripNonAlpha #go to stripNonAlpha
stripEnd:
la $a0, Buffer #save modified string into buffer
jr $ra #return
Any help would be appreciated.
.data
Buffer: .asciiz " " # 80 bytes in Buffer
intro: .asciiz "Hello, please enter a string of up to 80 characters. I will then tell you if that string was a palindrome!"
.text
main:
li $v0, 4 # print_string call number
la $a0, intro # pointer to string in memory
syscall
li $v0, 8 #syscall code for reading string
la $a0, Buffer #save read string into buffer
li $a1, 80 #string is 80 bytes long
syscall
li $s0, 0 #i = 0
li $t0, 80 #max for i to reach
la $a0, Buffer
jal stripNonAlpha
li $v0, 4 # print_string call number
la $a0, Buffer # pointer to string in memory
syscall
#################################
# stripNonAlpha method #
#################################
stripNonAlpha:
beq $s0, $t0, stripEnd #if i = 80 end
add $t4, $s0, $a0 #address of Buffer[i] in $t4
lb $s1, 0($t4) #load value of Buffer[i]
slti $t1, $s1, 48 #if ascii code is less than 48
bne $t1, $zero, strip #remove ascii character
slti $t1, $s1, 58 #if ascii code is greater than 57
#and
slti $t2, $s1, 65 #if ascii code is less than 65
slt $t3, $t1, $t2
bne $t3, $zero, strip #remove ascii character
slti $t1, $s1, 91 #if ascii code is greater than 90
#and
slti $t2, $s1, 97 #if ascii code is less than 97
slt $t3, $t1, $t2
bne $t3, $zero, strip #remove ascii character
slti $t1, $s1, 123 #if ascii character is greater than 122
beq $t1, $zero, strip #remove ascii character
addi $s0, $s0, 1 #i = i + 1
j stripNonAlpha #go to stripNonAlpha
strip:
add $t5, $s0, $a0 #address of Buffer[i] in $t5
sb $0, 0($t5) #Buffer[i] = 0
addi $s0, $s0, 1 #i = i + 1
j stripNonAlpha #go to stripNonAlpha
stripEnd:
la $a0, Buffer #save modified string into buffer
jr $ra #return