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New Contributor I

What is IMPLICIT UNDEFINED?

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I am reviewing some legacy Fortran code implementing a numerical algorithm and it contains the statement IMPLICIT UNDEFINED (A-H,O-Z). I have never come across such a statement before. Is it the same as IMPLICIT NONE? It should be fairly easy to comment out or replace.

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Black Belt

It is an old Sun Fortran

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It is an old Sun Fortran extension. You can replace it by IMPLICIT NONE and move on.

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Black Belt
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It is an old Sun Fortran

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It is an old Sun Fortran extension. You can replace it by IMPLICIT NONE and move on.

View solution in original post

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Valued Contributor III

An extension for sure, but

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New Contributor II

Take are that

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Take care that

IMPLICIT UNDEFINED (A-H,O-Z)

will leave I-N implicitly defined

IMPLICIT NONE

will undefine all variables.

For me, if it is legal :

IMPLICIT NONE

IMPLICIT INTEGER (I-N)

will only be equivalent to

IMPLICIT UNDEFINED (A-H,O-Z)

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Black Belt

It is legal to have multiple

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It is legal to have multiple IMPLICIT statements as long as there is only one IMPLICIT NONE.

Steve (aka "Doctor Fortran") - https://stevelionel.com/drfortran
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New Contributor I

The two statements are not

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The two statements are not equivalent. One defines I,J,K,L,M and N as INTEGER while the other doesn't.

mecej4 wrote:

It is an old Sun Fortran extension. You can replace it by IMPLICIT NONE and move on.

John Alexiou
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New Contributor II

Hi

I presumed that if the IMPLICIT UNDEFINED (A-H,O-Z) statement was used in this code it was because the compiler used to compile it always define implicit types (A-H,O-Z) as real and (I-N) as integer as old compilers used to. So the aim of this statement was to keep integer variables defined.

Otherwise, the IMPLICIT NONE statement would have been used.

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