Character Intrinsics and Conditionals

Character Functions

These intrinsic functions operate on individual characters.

! Returns the integer in the character sequence corresponding to the single
! character c
ICHAR(C [,KIND])
! Same as ichar
IACHAR(C [,KIND])
! Returns the character corresponding to integer i
CHAR(I [,KIND])
! Same as char
ACHAR(I [,KIND])

String Functions

These intrinsic functions operate on strings of any length.

Length and Trimming

! Length of string (returns declared size for fixed-length strings)
LEN(STR)
! Length of string with trailing blanks removed
LEN_TRIM(STR)
! Returns new string with trailing blanks removed from argument
TRIM(STR)
! Concatenate multiple copies of the same string
REPEAT(STR,NCOPIES)

Alignment

These functions adjust the appearance of a string.

! Adjust left by removing leading spaces
ADJUSTL(STR)
! Adjust right by removing trailing spaces. Pad front if necessary.
ADJUSTR(STR)

Example

character(len=15) :: lang
lang="Fortran"
print *, lang
print *, adjustl(lang)
print *, adjustr(lang)

The default is to left justify the string.

Searching

Search for characters and substrings.

! In these, the BACK option, if present, must be logical.
! Return starting indext of SUBSTR from left (from right with BACK)
!   or zero if SUBSTR not present.
INDEX(STR, SUBSTR[, BACK [, KIND]])
! If any of SET is in STR, return leftmost (rightmost with BACK) position in STR
SCAN(STR, SET[, BACK [, KIND]])
! Check whether all the characters of SET are in STR, return first location 
   of a character _not_ in SET, or zero if all are present.
! VERIFY(STR, SET[, BACK [, KIND]])

Example

character(len=15) :: lang
character(len=5) :: ort
lang="Fortran"
ort="ort"
print *, index(lang,'f')
print *, index(lang,'F')
print *, scan(lang, ort)
print *, verify(lang, ort)

Character Comparison Operators

Strings can be compared to one another. These operators use lexical ordering, which is based on the ordering in the character set along with rules for comparing multiple-character strings one character at a time. The usual operators ==,/=,<,<=,>,>= may be used, as well as the functions below. The standard operators use ASCII ordering, whereas the functions use the character set on a particular platform, which may not use ASCII ordering.

String comparisons are case sensitive.

! Returns .true. if stringA is lexically greater than or equal to stringB, 
!   otherwise returns .false.
LGE(STRINGA,STRINGB)
! Lexically greater than to stringB, 
LGT(STRINGA,STRINGB)
! Returns .true. if stringA is lexically less than or equal to stringB, 
!  otherwise returns.false.
LLE(STRINGA,STRINGB)
! Lexically less than string B 
LLT(STRINGA,STRINGB)

Example

print *, lang=="Fortran"
print *, lang=="fortran"
print *, "Fortran"<"fortran"  !surprise!
print *, "2.">="2.0" 
print *, lle("2.","2.0") 
print *, "1"<="10"  
print *, llt("1","10")  
print *, "1"<=" 1"