Numbers

StringiFor integrates with PENF (Portable Environment for Fortran) to provide portable numeric kind parameters and seamless string–number conversion.

PENF Kind Parameters

use stringifor re-exports all PENF kind parameters:

Parameter	Type	Bytes
I1P	integer	1
I2P	integer	2
I4P	integer	4
I8P	integer	8
R4P	real	4
R8P	real	8
R16P	real	16 (optional, requires -Dr16p)

Assigning Numbers to Strings

The assignment(=) operator is overloaded for all PENF integer and real kinds:

use stringifor
type(string) :: s

! Integer assignment
s = 127_I1P
print "(A)", s//''   ! +127

s = -32768_I2P
print "(A)", s//''   ! -32768

s = 1000000_I4P
print "(A)", s//''   ! +1000000

! Real assignment
s = 3.021e6_R4P
print "(A)", s//''   ! +0.302100E+07

s = -1.23456789_R8P
print "(A)", s//''   ! -1.23456789000000E+00

Inquiring String Content

use stringifor
type(string) :: s

s = '3.14'
print "(L1)", s%is_number()    ! T
print "(L1)", s%is_real()      ! T
print "(L1)", s%is_integer()   ! F

s = '42'
print "(L1)", s%is_number()    ! T
print "(L1)", s%is_integer()   ! T
print "(L1)", s%is_real()      ! F

s = 'hello'
print "(L1)", s%is_number()    ! F
print "(L1)", s%is_digit()     ! F

s = '0123'
print "(L1)", s%is_digit()     ! T  (all characters are digits)

Casting Strings to Numbers

The to_number method casts a string to any PENF numeric kind. The kind argument selects the target type:

use stringifor
type(string) :: s

s = "3.4e9"

if (s%is_real()) then
  print "(E13.6)", s%to_number(kind=1._R4P)   !  0.340000E+10
  print "(E20.12)", s%to_number(kind=1._R8P)  !  0.340000000000E+10
end if

s = "42"
if (s%is_integer()) then
  print "(I0)", s%to_number(kind=1_I4P)       ! 42
end if

INFO

The kind argument is only used to select the return type — its value is ignored. Pass any literal of the target kind (e.g., 1._R8P, 0_I4P).

Complete Example

use stringifor
implicit none
type(string) :: s
real(R8P)    :: x
integer(I4P) :: n

! String → number → string round-trip
s = "2.718281828"
x = s%to_number(kind=1._R8P)
s = x                           ! re-assign the number back to a string
print "(A)", s//''              ! +2.71828182800000E+00

! Parse and compare
s = "100"
if (s%is_integer()) then
  n = s%to_number(kind=1_I4P)
  if (n > 50) print "(A)", "Greater than 50"
end if