SLA_INTIN

Decode an Integer Number

ACTION:
Convert free-format input into an integer.
CALL:
CALL sla_INTIN (STRING, NSTRT, IRESLT, JFLAG)
GIVEN:

STRING

C

string containing number to be decoded

NSTRT

I

pointer to where decoding is to commence

IRESLT

I

current value of result


RETURNED:

NSTRT

I

advanced to next number

IRESLT

I

result

JFLAG

I

status: 1 = OK, 0 = +OK, 1 = null result, 2 = error


NOTES:
(1)
The reason sla_INTIN has separate ‘OK’ status values for + and is to enable minus zero to be detected. This is of crucial importance when decoding mixed-radix numbers. For example, an angle expressed as degrees, arcminutes and arcseconds may have a leading minus sign but a zero degrees field.
(2)
A TAB is interpreted as a space. n.b. The test for TAB is ASCII-specific.
(3)
The basic format is the sequence of fields ±n, where ± is a sign character ‘+’ or ‘’, and n means a string of decimal digits.
(4)
Spaces:
  • Leading spaces are ignored.
  • Spaces between the sign and the number are allowed.
  • Trailing spaces are ignored; the first signifies end of decoding and subsequent ones are skipped.
(5)
Delimiters:
  • Any character other than +,,0-9 or space may be used to signal the end of the number and terminate decoding.
  • Comma is recognized by sla_INTIN as a special case; it is skipped, leaving the pointer on the next character. See 9, below.
  • Decoding will in all cases terminate if end of string is reached.
(6)
The sign is optional. The default is +.
(7)
A null result occurs when the string of characters being decoded does not begin with +, or 0-9, or consists entirely of spaces. When this condition is detected, JFLAG is set to 1 and IRESLT is left untouched.
(8)
NSTRT = 1 for the first character in the string.
(9)
On return from sla_INTIN, NSTRT is set ready for the next decode – following trailing blanks and any comma. If a delimiter other than comma is being used, NSTRT must be incremented before the next call to sla_INTIN, otherwise all subsequent calls will return a null result.
(10)
Errors (JFLAG=2) occur when:
  • there is a + or but no number; or
  • the number is greater than 231 1.
(11)
When an error has been detected, NSTRT is left pointing to the character following the last one used before the error came to light.
(12)
See also sla_FLOTIN and sla_DFLTIN.