SLA_INTIN - Decode an Integer Number   

ACTION:

Convert free-format input into an integer.

CALL:

CALL sla_INTIN (STRING, NSTRT, IRESLT, JFLAG)

GIVEN:

STRING string containing number to be decoded

NSTRT I pointer to where decoding is to commence

IRESLT I current value of result

RETURNED:

NSTRT 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 $\pm n$, where $\pm$ 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.