user: Demonstrate the C code that generates the assembly output below:

```asm
<getop>:
  endbr64
  push   %r13
  push   %r12
  push   %rbp
  push   %rbx
  mov    %rdi,%rbx
  sub    $0x8,%rsp
  nopl   0x0(%rax)
L129:
  xor    %eax,%eax
  call   <getch@plt>
  mov    %al,(%rbx)
  mov    %eax,%r12d
  cmp    $0x20,%eax
  je     L129
  cmp    $0x9,%eax
  je     L129
  movb   $0x0,0x1(%rbx)
  movsbl %al,%ebp
  mov    %ebp,%edi
  call   <isdigit@plt>
  test   %rax,%rax
  jne    L57
  lea    -0x2d(%r12),%eax
  cmp    $0x1,%eax
  jbe    L57
  mov    %r12d,%eax
  xor    %r13d,%r13d
  and    $0xffffffdf,%eax
  cmp    $0x45,%eax
  jne    L85
L24:
  mov    %ebp,%edi
  call   <isdigit@plt>
  test   %rax,%rax
  je     L164
L8:
  lea    0x1(%r13),%ebp
  movslq %ebp,%rbp
  nopl   0x0(%rax)
L165:
  xor    %eax,%eax
  mov    %ebp,%r13d
  call   <getch@plt>
  mov    %al,(%rbx,%rbp,1)
  movsbl %al,%edi
  mov    %eax,%r12d
  add    $0x1,%rbp
  call   <isdigit@plt>
  test   %rax,%rax
  jne    L165
L164:
  cmp    $0x2e,%r12d
  je     L29
L113:
  mov    %r12d,%eax
  and    $0xffffffdf,%eax
  cmp    $0x45,%eax
  movslq %r13d,%rax
  je     L154
  add    %rax,%rbx
  mov    D1(%rip),%rax
  movb   $0x0,(%rbx)
  cmp    %r12d,(%rax)
  je     L78
L37:
  mov    %r12d,%edi
  mov    $0x30,%r12d
  call   <ungetch@plt>
L85:
  add    $0x8,%rsp
  mov    %r12d,%eax
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  ret
  nopw   0x0(%rax,%rax,1)
L57:
  xor    %r13d,%r13d
  cmp    $0x2d,%r12d
  jne    L24
  xor    %eax,%eax
  call   <getch@plt>
  movsbl %al,%ebp
  mov    %eax,%r13d
  mov    %ebp,%edi
  call   <isdigit@plt>
  test   %rax,%rax
  je     L176
  mov    %r13b,0x1(%rbx)
  mov    %ebp,%edi
  mov    %r13d,%r12d
  mov    $0x1,%r13d
  call   <isdigit@plt>
  test   %rax,%rax
  je     L164
  jmp    L8
  nopl   0x0(%rax)
L154:
  lea    0x1(%rbx,%rax,1),%rbp
  nopl   (%rax)
L179:
  xor    %eax,%eax
  mov    %rbp,%rbx
  add    $0x1,%rbp
  call   <getch@plt>
  mov    %al,-0x1(%rbp)
  movsbl %al,%edi
  mov    %eax,%r12d
  call   <isdigit@plt>
  test   %rax,%rax
  jne    L179
  mov    D1(%rip),%rax
  movb   $0x0,(%rbx)
  cmp    %r12d,(%rax)
  jne    L37
L78:
  add    $0x8,%rsp
  mov    $0x30,%r12d
  pop    %rbx
  mov    %r12d,%eax
  pop    %rbp
  pop    %r12
  pop    %r13
  ret
L29:
  lea    0x1(%r13),%ebp
  movslq %ebp,%rbp
  nopw   0x0(%rax,%rax,1)
L181:
  xor    %eax,%eax
  mov    %ebp,%r13d
  call   <getch@plt>
  mov    %al,(%rbx,%rbp,1)
  movsbl %al,%edi
  mov    %eax,%r12d
  add    $0x1,%rbp
  call   <isdigit@plt>
  test   %rax,%rax
  jne    L181
  jmp    L113
L176:
  mov    %r13d,%edi
  call   <ungetch@plt>
  jmp    L85
```

assistant: ```c
int getop(char s[]) {
  int i, c;
  do {
    s[0] = c = getch();
  } while (c == ' ' || c == '\t');
  s[1] = '\0';
  if (!isdigit(c) && c != '.' && c != '-' && c != 'e' && c != 'E')
    return c;
  i = 0;
  if (c == '-') {
    if (isdigit(c = getch())) {
      s[++i] = c;
    } else {
      ungetch(c);
      return '-';
    }
  }
  if (isdigit(c))
    while (isdigit(s[++i] = c = getch()))
      ;
  if (c == '.')
    while (isdigit(s[++i] = c = getch()))
      ;
  if (c == 'e' || c == 'E')
    while (isdigit(s[++i] = c = getch()))
      ;
  s[i] = '\0';
  if (c != EOF)
    ungetch(c);
  return '0';
}
```