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Implement the UNIX seq command in python. Source code for the original seq command is included in seq.c. Specification for the python program is in seqspec.txt. Compliance level 1 must be completed in the next 8 hours, very urgent. This pledge is for compliance level 1 only.
/* seq – pr
int
sequence of numbers to standard output.
Copyright (C) 1994-2013 Free Software Foundation, Inc.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see
/* Written by Ulrich Drepper. */
#include
#include
#include
#include
#include “system.h”
#include “c-strtod.h”
#include “error.h”
#include “quote.h”
#include “xstrtod.h”
/* Roll our own isfinite rather than using
have to worry about linking -lm just for isfinite. */
#ifndef isfinite
# define isfinite(x) ((x) * 0 == 0)
#endif
/* The official name of this program (e.g., no ‘g’ prefix). */
#define PROGRAM_NAME “seq”
#define AUTHORS proper_name (“Ulrich Drepper”)
/* If true print all number with equal width. */
static bool
equal_width;
/* The string used to separate two numbers. */
static char const *
separator;
/* The string output after all numbers have been output.
Usually “\n” or “\0”. */
static char const terminator[] = “\n”;
static struct option const long_options[] =
{
{ “equal-width”, no_argument, NULL, ‘w’
}
,
{ “format”, required_argument, NULL, ‘f’},
{ “separator”, required_argument, NULL, ‘s’},
{GETOPT_HELP_OPTION_DECL},
{GETOPT_VERSION_OPTION_DECL},
{ NULL, 0, NULL, 0}
};
void
usage (int status)
{
if (status != EXIT_SUCCESS)
emit_try_help ();
else
{
printf (_(“\
Usage: %s [OPTION]… LAST
\n\
or: %s [OPTION]… FIRST LAST\n\
or: %s [OPTION]… FIRST INCREMENT LAST\n\
“), program_name, program_name, program_name);
fputs (_(“\
Print numbers from FIRST to LAST, in steps of INCREMENT.\n\
“), stdout);
emit_mandatory_arg_note ();
fputs (_(“\
-f, –format=FORMAT use printf style floating-point FORMAT\n\
-s, –separator=STRING use STRING to separate numbers (default: \\n)\n\
-w, –equal-width equalize width by padding with leading zeroes\n\
“), stdout);
fputs (HELP_OPTION_DESCRIPTION, stdout);
fputs (VERSION_OPTION_DESCRIPTION, stdout);
fputs (_(“\
\n\
If FIRST or INCREMENT is omitted, it defaults to 1. That is, an\n\
omitted INCREMENT defaults to 1 even when LAST is smaller than FIRST.\n\
The sequence of numbers ends when the sum of the current number and\n\
INCREMENT would become greater than LAST.\n\
FIRST, INCREMENT, and LAST are interpreted as floating point values.\n\
INCREMENT is usually positive if FIRST is smaller than LAST, and\n\
INCREMENT is usually negative if FIRST is greater than LAST.\n\
“), stdout);
fputs (_(“\
FORMAT must be suitable for printing one argument of type ‘double’;\n\
it defaults to %.PRECf if FIRST, INCREMENT, and LAST are all fixed point\n\
decimal numbers with maximum precision PREC, and to %g otherwise.\n\
“), stdout);
emit_ancillary_info ();
}
exit (status);
}
/* A command-line operand. */
struct operand
{
/* Its value, converted to ‘long double’. */
long double value;
/* Its print width, if it were printed out in a form similar to its
input form. An input like “-.1” is treated like “-0.1”, and an
input like “1.” is treated like “1”, but otherwise widths are
left alone. */
size_t width;
/* Number of digits after the decimal point, or INT_MAX if the
number can’t easily be expressed as a fixed-point number. */
int precision;
};
typedef struct operand operand;
/* Description of what a number-generating format will generate. */
struct layout
{
/* Number of bytes before and after the number. */
size_t prefix_len;
size_t suffix_len;
};
/* Read a long double value from the command line.
Return if the string is correct else signal error. */
static operand
scan_arg (const char *arg)
{
operand ret;
if (! xstrtold (arg, NULL, &ret.value, c_strtold))
{
error (0, 0, _(“invalid floating point argument: %s”), arg);
usage (EXIT_FAILURE);
}
/* We don’t output spaces or ‘+’ so don’t include in width */
while (isspace (to_uchar (*arg)) || *arg == ‘+’)
arg++;
ret.width = strlen (arg);
ret.precision = INT_MAX;
if (! arg[strcspn (arg, “xX”)] && isfinite (ret.value))
{
char const *decimal_point = strchr (arg, ‘.’);
if (! decimal_point)
ret.precision = 0;
else
{
size_t fraction_len = strcspn (decimal_point + 1, “eE”);
if (fraction_len <= INT_MAX)
ret.precision = fraction_len;
ret.width += (fraction_len == 0 /* #. -> # */
? -1
: (decimal_point == arg /* .# -> 0.# */
|| ! ISDIGIT (decimal_point[-1]))); /* -.# -> 0.# */
}
char const *e = strchr (arg, ‘e’);
if (! e)
e = strchr (arg, ‘E’);
if (e)
{
long exponent = strtol (e + 1, NULL, 10);
ret.precision += exponent < 0 ? -exponent : 0;
/* Don’t account for e…. in the width since this is not output. */
ret.width -= strlen (arg) – (e – arg);
/* Adjust the width as per the exponent. */
if (exponent < 0)
{
if (decimal_point)
{
if (e == decimal_point + 1) /* undo #. -> # above */
ret.width++;
}
else
ret.width++;
exponent = -exponent;
}
ret.width += exponent;
}
}
return ret;
}
/* If FORMAT is a valid printf format for a double argument, return
its long double equivalent, allocated from dynamic storage, and
store into *LAYOUT a description of the output layout; otherwise,
report an error and exit. */
static char const *
long_double_format (char const *fmt, struct layout *layout)
{
size_t i;
size_t prefix_len = 0;
size_t suffix_len = 0;
size_t length_modifier_offset;
bool has_L;
for (i = 0; ! (fmt[i] == ‘%’ && fmt[i + 1] != ‘%’); i += (fmt[i] == ‘%’) + 1)
{
if (!fmt[i])
error (EXIT_FAILURE, 0,
_(“format %s has no %% directive”), quote (fmt));
prefix_len++;
}
i++;
i += strspn (fmt + i, “-+#0 ‘”);
i += strspn (fmt + i, “0123456789”);
if (fmt[i] == ‘.’)
{
i++;
i += strspn (fmt + i, “0123456789”);
}
length_modifier_offset = i;
has_L = (fmt[i] == ‘L’);
i += has_L;
if (fmt[i] == ‘\0’)
error (EXIT_FAILURE, 0, _(“format %s ends in %%”), quote (fmt));
if (! strchr (“efgaEFGA”, fmt[i]))
error (EXIT_FAILURE, 0,
_(“format %s has unknown %%%c directive”), quote (fmt), fmt[i]);
for (i++; ; i += (fmt[i] == ‘%’) + 1)
if (fmt[i] == ‘%’ && fmt[i + 1] != ‘%’)
error (EXIT_FAILURE, 0, _(“format %s has too many %% directives”),
quote (fmt));
else if (fmt[i])
suffix_len++;
else
{
size_t format_size = i + 1;
char *ldfmt = xmalloc (format_size + 1);
memcpy (ldfmt, fmt, length_modifier_offset);
ldfmt[length_modifier_offset] = ‘L’;
strcpy (ldfmt + length_modifier_offset + 1,
fmt + length_modifier_offset + has_L);
layout->prefix_len = prefix_len;
layout->suffix_len = suffix_len;
return ldfmt;
}
}
/* Actually print the sequence of numbers in the specified range, with the
given or default stepping and format. */
static void
print_numbers (char const *fmt, struct layout layout,
long double first, long double step, long double last)
{
bool out_of_range = (step < 0 ? first < last : last < first);
if (! out_of_range)
{
long double x = first;
long double i;
for (i = 1; ; i++)
{
long double x0 = x;
printf (fmt, x);
if (out_of_range)
break;
x = first + i * step;
out_of_range = (step < 0 ? x < last : last < x);
if (out_of_range)
{
/* If the number just past LAST prints as a value equal
to LAST, and prints differently from the previous
number, then print the number. This avoids problems
with rounding. For example, with the x86 it causes
“seq 0 0.000001 0.000003” to print 0.000003 instead
of stopping at 0.000002. */
bool print_extra_number = false;
long double x_val;
char *x_str;
int x_strlen;
setlocale (LC_NUMERIC, “C”);
x_strlen = asprintf (&x_str, fmt, x);
setlocale (LC_NUMERIC, “”);
if (x_strlen < 0)
xalloc_die ();
x_str[x_strlen – layout.suffix_len] = ‘\0’;
if (xstrtold (x_str + layout.prefix_len, NULL, &x_val, c_strtold)
&& x_val == last)
{
char *x0_str = NULL;
if (asprintf (&x0_str, fmt, x0) < 0)
xalloc_die ();
print_extra_number = !STREQ (x0_str, x_str);
free (x0_str);
}
free (x_str);
if (! print_extra_number)
break;
}
fputs (separator, stdout);
}
fputs (terminator, stdout);
}
}
/* Return the default format given FIRST, STEP, and LAST. */
static char const *
get_default_format (operand first, operand step, operand last)
{
static char format_buf[sizeof “%0.Lf” + 2 * INT_STRLEN_BOUND (int)];
int prec = MAX (first.precision, step.precision);
if (prec != INT_MAX && last.precision != INT_MAX)
{
if (equal_width)
{
/* increase first_width by any increased precision in step */
size_t first_width = first.width + (prec – first.precision);
/* adjust last_width to use precision from first/step */
size_t last_width = last.width + (prec – last.precision);
if (last.precision && prec == 0)
last_width–; /* don’t include space for ‘.’ */
if (last.precision == 0 && prec)
last_width++; /* include space for ‘.’ */
if (first.precision == 0 && prec)
first_width++; /* include space for ‘.’ */
size_t width = MAX (first_width, last_width);
if (width <= INT_MAX)
{
int w = width;
sprintf (format_buf, “%%0%d.%dLf”, w, prec);
return format_buf;
}
}
else
{
sprintf (format_buf, “%%.%dLf”, prec);
return format_buf;
}
}
return “%Lg”;
}
/* The NUL-terminated string S0 of length S_LEN represents a valid
non-negative decimal integer. Adjust the string and length so
that the pair describe the next-larger value. */
static void
incr (char **s0, size_t *s_len)
{
char *s = *s0;
char *endp = s + *s_len – 1;
do
{
if ((*endp)++ < '9')
return;
*endp– = ‘0’;
}
while (endp >= s);
*–(*s0) = ‘1’;
++*s_len;
}
/* Compare A and B (each a NUL-terminated digit string), with lengths
given by A_LEN and B_LEN. Return +1 if A < B, -1 if B < A, else 0. */
static int
cmp (char const *a, size_t a_len, char const *b, size_t b_len)
{
if (a_len < b_len)
return -1;
if (b_len < a_len)
return 1;
return (strcmp (a, b));
}
/* Trim leading 0’s from S, but if S is all 0’s, leave one.
Return a pointer to the trimmed string. */
static char const * _GL_ATTRIBUTE_PURE
trim_leading_zeros (char const *s)
{
char const *p = s;
while (*s == ‘0’)
++s;
/* If there were only 0’s, back up, to leave one. */
if (!*s && s != p)
–s;
return s;
}
/* Print all whole numbers from A to B, inclusive — to stdout, each
followed by a newline. If B < A, return false and print nothing.
Otherwise, return true. */
static bool
seq_fast (char const *a, char const *b)
{
/* Skip past any leading 0’s. Without this, our naive cmp
function would declare 000 to be larger than 99. */
a = trim_leading_zeros (a);
b = trim_leading_zeros (b);
size_t p_len = strlen (a);
size_t q_len = strlen (b);
size_t n = MAX (p_len, q_len);
char *p0 = xmalloc (n + 1);
char *p = memcpy (p0 + n – p_len, a, p_len + 1);
char *q0 = xmalloc (n + 1);
char *q = memcpy (q0 + n – q_len, b, q_len + 1);
bool ok = cmp (p, p_len, q, q_len) <= 0;
if (ok)
{
/* Buffer at least this many numbers per fwrite call.
This gives a speed-up of more than 2x over the unbuffered code
when printing the first 10^9 integers. */
enum {N = 40};
char *buf = xmalloc (N * (n + 1));
char const *buf_end = buf + N * (n + 1);
char *z = buf;
/* Write first number to buffer. */
z = mempcpy (z, p, p_len);
/* Append separator then number. */
while (cmp (p, p_len, q, q_len) < 0)
{
*z++ = *separator;
incr (&p, &p_len);
z = mempcpy (z, p, p_len);
/* If no place for another separator + number then
output buffer so far, and reset to start of buffer. */
if (buf_end – (n + 1) < z)
{
fwrite (buf, z – buf, 1, stdout);
z = buf;
}
}
/* Write any remaining buffered output, and the terminator. */
*z++ = *terminator;
fwrite (buf, z – buf, 1, stdout);
IF_LINT (free (buf));
}
free (p0);
free (q0);
return ok;
}
/* Return true if S consists of at least one digit and no non-digits. */
static bool _GL_ATTRIBUTE_PURE
all_digits_p (char const *s)
{
size_t n = strlen (s);
return ISDIGIT (s[0]) && n == strspn (s, “0123456789”);
}
int
main (int argc, char **argv)
{
int optc;
operand first = { 1, 1, 0 };
operand step = { 1, 1, 0 };
operand last;
struct layout layout = { 0, 0 };
/* The printf(3) format used for output. */
char const *format_str = NULL;
initialize_main (&argc, &argv);
set_program_name (argv[0]);
setlocale (LC_ALL, “”);
bindtextdomain (PACKAGE, LOCALEDIR);
textdomain (PACKAGE);
atexit (close_stdout);
equal_width = false;
separator = “\n”;
/* We have to handle negative numbers in the command line but this
conflicts with the command line arguments. So explicitly check first
whether the next argument looks like a negative number. */
while (optind < argc)
{
if (argv[optind][0] == ‘-‘
&& ((optc = argv[optind][1]) == ‘.’ || ISDIGIT (optc)))
{
/* means negative number */
break;
}
optc = getopt_long (argc, argv, “+f:s:w”, long_options, NULL);
if (optc == -1)
break;
switch (optc)
{
case ‘f’:
format_str = optarg;
break;
case ‘s’:
separator = optarg;
break;
case ‘w’:
equal_width = true;
break;
case_GETOPT_HELP_CHAR;
case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
default:
usage (EXIT_FAILURE);
}
}
unsigned int n_args = argc – optind;
if (n_args < 1)
{
error (0, 0, _(“missing operand”));
usage (EXIT_FAILURE);
}
if (3 < n_args)
{
error (0, 0, _(“extra operand %s”), quote (argv[optind + 3]));
usage (EXIT_FAILURE);
}
if (format_str)
format_str = long_double_format (format_str, &layout);
if (format_str != NULL && equal_width)
{
error (0, 0, _(“format string may not be specified”
” when printing equal width strings”));
usage (EXIT_FAILURE);
}
/* If the following hold:
– no format string, [FIXME: relax this, eventually]
– integer start (or no start)
– integer end
– increment == 1 or not specified [FIXME: relax this, eventually]
then use the much more efficient integer-only code. */
if (all_digits_p (argv[optind])
&& (n_args == 1 || all_digits_p (argv[optind + 1]))
&& (n_args < 3 || (STREQ ("1", argv[optind + 1])
&& all_digits_p (argv[optind + 2])))
&& !equal_width && !format_str && strlen (separator) == 1)
{
char const *s1 = n_args == 1 ? “1” : argv[optind];
char const *s2 = argv[optind + (n_args – 1)];
if (seq_fast (s1, s2))
exit (EXIT_SUCCESS);
/* Upon any failure, let the more general code deal with it. */
}
last = scan_arg (argv[optind++]);
if (optind < argc)
{
first = last;
last = scan_arg (argv[optind++]);
if (optind < argc)
{
step = last;
last = scan_arg (argv[optind++]);
}
}
if (first.precision == 0 && step.precision == 0 && last.precision == 0
&& 0 <= first.value && step.value == 1 && 0 <= last.value
&& !equal_width && !format_str && strlen (separator) == 1)
{
char *s1;
char *s2;
if (asprintf (&s1, “%0.Lf”, first.value) < 0)
xalloc_die ();
if (asprintf (&s2, “%0.Lf”, last.value) < 0)
xalloc_die ();
if (seq_fast (s1, s2))
{
IF_LINT (free (s1));
IF_LINT (free (s2));
exit (EXIT_SUCCESS);
}
free (s1);
free (s2);
/* Upon any failure, let the more general code deal with it. */
}
if (format_str == NULL)
format_str = get_default_format (first, step, last);
print_numbers (format_str, layout, first.value, step.value, last.value);
exit (EXIT_SUCCESS);
}
Specification of the “sequ” command
Copyright © 2013 Bart Massey
Revision 0: 1 October 2013
This specification describes the “universal sequence” command sequ. The sequ command is a backward-compatible set of extensions to the UNIX [seq](http://www.gnu.org/software/coreutils/manual/html_node/seq-invocation.html) command. There are many implementations of seq out there: this specification is built on the seq supplied with GNU Coreutils version 8.21.
The seq command emits a monotonically increasing sequence of numbers. It is most commonly used in shell scripting:
TOTAL=0
for i in `seq 1 10`
do
TOTAL=`expr $i + $TOTAL`
done
echo $TOTAL
prints 55 on standard output. The full sequ command does this basic counting operation, plus much more.
This specification of sequ is in several stages, known as compliance levels. Each compliance level adds required functionality to the sequ specification. Level 1 compliance is equivalent to the Coreutils seq command.
The usual specification language applies to this document: MAY, SHOULD, MUST (and their negations) are used in the standard fashion.
Wherever the specification indicates an error, a conforming sequ implementation MUST immediately issue appropriate error message specific to the problem. The implementation then MUST exit, with a status indicating failure to the invoking process or system. On UNIX systems, the error MUST be indicated by exiting with status code 1.
When a conforming sequ implementation successfully completes its output, it MUST immediately exit, with a status indicating success to the invoking process or systems. On UNIX systems, success MUST be indicated by exiting with status code 0.
Compliance Level 0
Compliance Level 0 of sequ requires absolute minimum functionality. A CL0 sequ MUST accept exactly two command-line arguments. Each argument SHOULD be a representation of an integer value. Any other supplied argument syntax is an error.
If the first integer argument is numerically greater than the second, the sequ command MUST emit no output. Otherwise, sequ MUST print on its output each of the integers between the first and second argument, inclusive. Each output integer MUST be on a line by itself, that is, a line terminated with an appropriate line terminator for the host environment.
Compliance Level 1
Compliance Level 1 of sequ adds the full functionality of GNU Coreutils seq. This includes the “–format”, “–separator”, “–equal-width”, “–help” and “–version” arguments (as well as the one-character abbreviations of these), the increment argument, and support for floating-point numbers. The sequ initialization and increment arguments are now optional, as per the seq spec.
The sequ “–format” specifier MAY format floating-point numbers differently than seq, but it MUST follow some well-described and reasonable floating-point formatting standard.
Backslash-escapes in the “-s” argument string MUST be processed as in C printf(3).
Start a text file of notes on what you’re about to do. As you work on this assignment, make notes about you findings and progress. You will turn in your notes at the end.
Read CL1 of the sequ spec. Note down any questions and concerns you have about it.
Write tests for CL1 of sequ. Be sure to have enough tests to catch problems with your implementation.
Write pseudocode for any parts of CL1 of sequ that you think need it. Check your pseudocode into the repo.
Write CL1 of sequ. Verify that it passes your tests. Record test results and debugging steps in your notes.
Compliance Level 2
Compliance Level 2 of sequ adds additional convenience arguments for formatting.
The arguments that MUST be accepted are as follows:
-W, –words: Output the sequence as a single space-separated line. Equivalent to “-s ‘ ‘”.
-p, –pad : Output the sequence with elements padded on the left to be all of equal width: the pad character is given by the single-char pad string . Backslash-escapes in MUST be processed as in C printf(3).
Note that the “-w” command of level 2 is equivalent to “-p ‘0’”.
-P, –pad-spaces: Output the sequence with elements padded with spaces on the left to be all of equal width. Equivalent to “-p ‘ ‘”.
Compliance Level 3
Compliance Level 3 of sequ adds the ability to have sequences of types other than floating-point numbers.
Specifically, CL3 sequ MUST accept as arguments and output as results: arbitrary-precision integers, single lowercase alphabetic (ASCII) letters, single uppercase alphabetic (ASCII) letters, and lowercase or uppercase unsigned Roman Numerals.
The sequ command MUST accept a new flag, “–format-word” or “-F”, that takes a one-word argument indicating the type of the sequence. The sequ command MUST accept the format-word arguments “arabic” (for integers), “floating”, “alpha” (for letters), “ALPHA”, “roman” or “ROMAN”; the all-uppercase variants indicate uppercase sequences.
The sequ command MUST accept limit arguments (start, end, and increment) in the format consistent with the format-word. Arabic limit arguments MAY be “promoted” to Roman Numerals when Roman output is requested. The increment argument for alpha formats MUST be arabic. Otherwise, the limit arguments MUST be in the same format as the format-word. When no format-word is given, the format MUST be inferred from the format of the mandatory end argument.
Compliance Level 4
Compliance Level 4 of sequ adds the ability to number the lines of a textfile presented on the input.
CL4 sequ MUST accept the “–number-lines” / “-n” argument. This argument indicates that, rather than outputting the sequence on standard output, sequ will act as a filter, numbering lines of a file read from standard input to standard output. Each line “number” will be in the format specified by the “–format-word” argument, or inferred from the start or increment limit argument if the “–format-word” argument is not supplied. The end argument is irrelevant when “–number-lines” is supplied; it MUST NOT be accepted. The separator between the line number and the line may be given by the “–separator” argument, defaulting to space.
Compliance Level 5
Compliance Level 5 of sequ adds the ability to infer a sequence from a given prefix.
As an alternative to the limit arguments of previous Compliance Levels, CL5 sequ may accept a sequence specifier of the form:
value [value] [value] … “..” value
When the “..” argument is present, the non-flag arguments MUST be parsed in inference mode.
In inference mode, sequ picks a best match for the pattern (partial sequence of values leading up to the “..”), and then continues the sequence until the end value (after the “..”) is succeeded.
